On an afternoon in June while wildfire smoke enveloped Manhattan, people lined up outside Irving Plaza — some before dawn, some sporting face masks, some fresh off red-eye flights — to see Dave Matthews. That night, the 56-year-old balladeer was playing a rare solo gig celebrating his namesake band’s new album, “Walk Around the Moon.”

Josh Roberts, 42, a special-education teacher in Las Vegas, who has seen the Dave Matthews Band, or DMB, 523 times, stood in that line. Mr. Roberts estimates that he has spent $100,000 on tickets and travel since discovering the band as a struggling high school junior in 1995. “This band has songs about love, depression, sex, things that you connect to,” he said.

Mr. Matthews is the first to admit he doesn’t always get it right. “I’ve written lots of terrible lyrics,” he declared at the Four Seasons hotel in TriBeCa the next day, scanning a printout of a song generated by ChatGPT in the style of DMB. He cringed and added, “I would never say, ‘Grab my guitar, strumming with all my might.’”

Still, plucking his guitar with abandon is exactly what Mr. Matthews has done since 1991, when DMB established itself in Charlottesville, Va. DMB is the second-largest ticket-seller in the world, according to the trade publication Pollstar, which tracked the top touring artists of the last 40 years. Mr. Matthews believes that curiosity “about how to write a good song” may be one reason his band has stayed in the spotlight for more than three decades, attracting hundreds of thousands of concertgoers on their 45-stop summer 2023 tour.

Yet, the band’s ardent fan base contrasts with its paradoxical pop-culture standing: In 2020, the Dave Matthews Band was nominated by the Rock & Roll Hall of Fame for induction and was entered into a public voting contest, which the group won. The band, however, did not garner enough support from the organization’s voting committee and was not included in the nominees list for the next three years.

For a certain set of music enthusiasts born between 1970 to 2000, DMB is synonymous with summer. “When this time comes, I can’t wait for it. It’s the kid in me,” Mr. Roberts said on a follow-up call during a 17-hour drive from Wisconsin to New Hampshire to see two more DMB shows. “I have more friends through DMB than I do through high school and college.”

Since 1992, the band, or some iteration of it, has toured relentlessly from Memorial Day to “Labor Dave Weekend” and beyond (except in 2020, because of the pandemic). Superfans routinely follow DMB around for regional legs of tours. Many have seen hundreds of shows, displaying a band-as-religion level fandom with tattoos, license plates and jewelry professing their piety.

Coupled with DMB’s taping-friendly policy (fans are allowed to audio record shows with professional equipment) and its hippie reputation, the band’s music frequently gets lumped together with the Grateful Dead and Phish.

A lot of “Deadheads,” as the Grateful Dead fans affectionately call themselves, either gravitated toward DMB or Phish when the band’s lead songwriter, Jerry Garcia, died in 1995, said Jeff Travitz, 61, a franchise development manager in Downingtown, Pa., who has taped over 100 DMB concerts. The bands are each unique, he said, but they filled the same “major void” to meet up with friends, tape shows and trade recordings.

“I don’t think too much about what we replaced,” Mr. Matthews said. Still, he understands the Phish comparison. In general, he thinks ’90s music critics dismissed improvisation, which, as far as he is concerned, is the only quality these groups share. “We all got thrown into the same category, even though we’re all different,” he said. “What do they call it? Jam bands?”

Whatever it’s labeled, fans have gone to great lengths for DMB. In 1998, the band launched the Warehouse, its official fan association, which allows members to pre-order tickets before the public, enter contests and access a message board. “I literally stole my mom’s credit card to join,” Mr. Roberts, the teacher, said. He now spearheads a Facebook group of about 850 DMB followers. Multiple times a tour, he will buy extra pit tickets, which cost about $50 to $150, with his own money and distribute them among the group at face value to combat scalping. (Mr. Matthews, too, laments the current business of ticketing: “I think half the profits that the ticket brokers make should be given back to the theaters, artists or charity, because they make so much money, and they’re really just scalpers.”)

Ridge Richter, a 35-year-old airline-ramp agent in Columbus, Ohio, who has seen 160 shows, doesn’t have any tattoos himself but runs in a crowd of DMB-saturated limbs. “A lot of people, if they’re crazy enough, if Dave signs their arm at a show, they’ll get a tattoo that day,” said Mr. Richter, who also moonlights as a DMB party planner. For each tour, he has organized six or seven tailgates complete with DMB cover bands.

Such fanaticism invites detractors. Many stereotype the fans as pot-smoking, tie-dye touting former fraternity bros fawning over craft beers in parking lots between cornhole games. The pop-culture mockery is especially palpable with DMB. See the “Trepidation of the Dave Matthews Fan” bit from the comedian Marc Maron; the cool factor of Anthony Bourdain snarking their fan base odium; and “Saturday Night Live” skits imitating Mr. Matthews’ distinct warble. (Mr. Matthews says that “Bill Hader might be the best one.”)

“I feel like his music is just elevator music” said Jody Harper, 44, a technology executive at an arts nonprofit in Manhattan. “The way I see it, everybody hanging out together at DMB concerts are just a bunch of people that want to hang out in an elevator together.”

With more than 30 years in the music industry, Mr. Matthews knows you can’t please everyone. “If you make stuff, some people will like it, and some people won’t,” he said. “I don’t have to prove anything to anyone.” He divulged that even his beloved grandfather didn’t understand his music.

He continued: “For people that hate me, I would just say, ‘Ignore me. Don’t waste your time!’”

Mr. Matthews attributed the band’s enduring allure, in part, to offering fans a singular experience every night. “I think about people that love our music but aren’t crazy fans,” he said. “I want them to have the best time. And then I want to play music for people that love us deeply. I want to play for everyone.”

The group has about 1,100 titles in their catalog and a core rotation of about 275 songs. Set lists vary substantially, and there are guest musicians for a night or two throughout the tour, including Warren Haynes and Brandi Carlile, as well as lesser-known local acts.

Mr. Travitz, the manager in Pennsylvania, appreciates that the band covers songs and interpolates snippets of others into its tunes. Some covers include Pink Floyd’s “Money,” Talking Heads’ “Burning Down the House” and Neil Young’s “Hey Hey, My My.” “It always makes the show fun when they play a song you’re totally not expecting,” Mr. Travitz said.

Mr. Matthews said the rapport among members of the band and crew was paramount to DMB’s longevity. When the band is crafting set lists, Mr. Matthews said he prioritized giving “everyone a moment to shine.”

The band members’ different ages and backgrounds may also explain their long-lasting appeal, added Mr. Matthews, citing his upbringing in New York, England and South Africa. “We all experienced different versions of the world,” he said. “Great friendships often come from people that have very different experiences.”

To broaden his perspective, Mr. Matthews often leans on his children. His 21-year-old twin daughters are either “full of praise where they think it’s deserved” or “they’ll tell me as quickly, ‘This is not a good song’ or ‘I don’t buy those lyrics.’” Mr. Matthews recurrently finds himself asking them and his 16-year-old son about his place in the world from their Generation Z perspective.

Meghan Brennan, a 24-year-old customer service manager in Boston, is part of a crop of new admirers and has seen some 50 shows. “I’m definitely one of the younger big fans,” she said, adding that her peers “think that I’m insane for doing what I do, which I am.” Her sister, 18 months her junior, in particular, doesn’t get the obsession. She “just hates how much I like them,” Ms. Brennan said.

Traveling to see the band has marked what Ms. Brennan calls a transitional life stage of college and living on her own for the first time. She appreciates the friends she has made at tailgates and preshow meetups from Nashville to Hartford, Conn. Her DMB friends are older and can offer advice from a different perspective, she said.

Mr. Matthews’ values also resonate: “He really is vocal about the environment,” Ms. Brennan said. (They are the first band to be designated as a Goodwill Ambassador by The United Nations Environment Programme.)

Rob Bokon, a 48-year-old technology consultant in Cincinnati and a co-founder of DMBAlmanac.com, an encyclopedia website for the band, has attended 154 shows in 18 states and 44 venues. For Mr. Bokon, his DMB concert experience is a reflection of his entire career trajectory. When he was young, working as a pizza delivery boy and making minimum wage, Mr. Bokon said he could only afford local shows. He eventually made enough money to attend destination shows, but he and his friends couldn’t afford hotel rooms, so they would often drive six hours back home after concerts, “sometimes in the snow, sometimes on two-lane roads,” he said. Of course, DMB poured out of the car’s tinny speakers the entire way home. “It was the best.”

Mr. Bokon’s fascination began when he started collecting cassettes of the band’s concerts in 1998. He initially tracked DMB’s set lists in spreadsheets but after one of the band’s concerts in Washington in 2001, he and his friend Matías Niño, who is a programmer, decided to build a fan site. That fan site became the Almanac, which is known as, among fans, the band’s de facto encyclopedia.

Alexa Miller Hall, a 48-year-old sales executive in Pittsburgh who has seen 164 shows, is used to telling naysayers about the band’s global impact and defending the magic of a DMB show. It never gets old, said Ms. Miller Hall, who saw her first show in 1992, after becoming a passionate tape trader in college. She guesses she has traveled over 100,000 miles and spent nearly $200,000 to see the band, at least $60,000 of that on tickets alone. Coordinating tickets “is like a part-time job,” she said.

In 2012, Ms. Miller Hall met a bassist in a DMB cover band called Grux in the pit at a DMB concert in New Jersey. “We started holding hands” during the show, she said. In 2015, they married. (Meeting partners through message boards, tailgates or concerts is not uncommon; Ms. Miller Hall knows another married couple that met at that same show.)

Ms. Miller Hall said the most extreme thing she ever did for the band was camp out during a snowstorm with a group of friends before the band headlined “The Night Before” performance in Minnesota during the Super Bowl in February 2018. To get close to the stage, the group had planned to sleep outside the arena in the freezing temperatures. “Thankfully by the grace of a security guard,” she said, “they let us into the foyer area, and we spent the night with the cigarette butts and gum.”

As for Mr. Matthews, his desire to make the best of whatever muck or gold life throws his way can be traced to his father (a scientist he described as “brilliant beyond my understanding”), who died of cancer when he was 10. This is why, he said, “I feel it’s necessary to remind myself of our temporary nature.” While he is unsure whether his father would have liked his music, he thinks he would have appreciated that attitude.

Though Mr. Matthews can’t pinpoint exactly why the band has remained so popular, he believes that luck may have played some kind of role. “It’s just what has happened to us, as much as we’ve done it,” he said. “Some worms end up in beautiful, rich, wet soil, and some worms end up on the sidewalk on a hot, sunny day.”