What is going on with breast pockets on shirts? Where did they go on men’s shirts? And why do they still exist on women’s? How does any of this make any sense? — Kristine, Boston

Pockets are one of those seemingly small details that provoke an outsize amount of opinions and unexpectedly strong feelings — whether about the fact that women’s clothing doesn’t have more of them or the incredible disappearing breast pocket.

Because, yes, the breast pocket has been falling out of favor for a while now, at least when it comes to the case of dress shirts, where it has become a victim of both fashion and technology.

On J. Crew’s website, only two styles on the three pages of men’s dress shirts come with a breast pocket, while at Suitsupply, none of the classic shirts have breast pockets. Even at Brooks Brothers, purveyor of men’s wear tradition, which says it sells over four million shirts a year, according to Arthur Wayne, a spokesman, 40 percent of shirts are now sold without a breast pocket, a number that has been increasing over time.

A largely midcentury invention, the breast pocket became popular as vests fell out of fashion because men, who didn’t carry handbags, needed more places to store their stuff. If a wallet could be slipped into suit pants or jackets, the breast pocket turned out to be the perfect place to carry pens and stow eyeglasses.

Since the turn of the millennium, however, as writing implements have become less and less important and phones have replaced pocket protectors, which themselves started getting a not-entirely-appealing nerd rep, breast pockets have had a similarly diminished reason for being (that is, bulkier phones are more easily stashed in a pants pocket).

At the same time, slim-line silhouettes became more and more popular. As Michael Bastian, the creative director of Brooks Brothers, said when I asked, “For me, on a classic dress suit, no pocket feels more polished.” This is especially true if the shirt is worn under a jacket.