Why do runway models always look miserable? They always look as if they would bite your head off if you spoke to them. What’s wrong with smiling? Did they ever? And if so, when did things change? — Lisa, Baltimore

I get this question all the time from people who catch sight of runway photos during fashion month. In fact, designers do sometimes ask their models to smile. Giorgio Armani did it this season for his Emporio Armani show. Sonia Rykiel used to do it all the time. She even had her models skip down the catwalk to add extra zest. And it was almost always … terrifying.

The truth is, it’s awfully hard to maintain a believable expression of great joy when you are walking in front of hundreds, if not thousands, of strangers, all there to render their judgment on what you are wearing. When your shoes probably don’t fit, since they are samples, and you are concentrating very hard to avoid slipping or falling, and you are modeling chiffon in winter or leather in September, when it’s still 80 degrees, and you are partially blinded by the flashes of a zillion photographers.

Besides, while clothes are meant to make consumers feel good, they should also make them feel safe, strong, confident, protected. Michael Kors used to have posters backstage scrawled with phrases like “own the room” and “walk like you mean it” to inspire his models. That kind of pantomiming doesn’t always come with a beaming face. Smiling can make one seem like a supplicant, and fashion is supposed to make you feel powerful in your skin.

Little wonder, really, that when a happy face is required, it turns, very quickly, into a frozen rictus that doesn’t reach the eyes — a facial disjunction that can be very disturbing to watch. It’s hard to concentrate on clothes when you are wondering if the woman who is wearing them has a knife secreted somewhere.

That is why Tyra Banks always instructed the contestants on “America’s Next Top Model” to “smize,” a brain worm of a neologism for “smile with your eyes.” Smiling with your actual mouth for the length of a runway generally looks just plain weird.

Aside from a brief period in the 1970s when models like Pat Cleveland danced down the runways and won the Battle of Versailles, or the moment in 1991 when the supermodels from George Michael’s “Freedom!” strutted down the Versace runway lip syncing to the song, or that time in 1993 when Naomi Campbell fell off her Vivienne Westwood platforms and couldn’t help bursting into laughter, smiles have rarely been the runway expression of choice. Look at any vintage photo of a classic couture salon, like Chanel or Christian Dior, and the mannequins are entirely po-faced.

And remember: The absence of a smile is not the same thing as the absence of attitude.

Your Style Questions, Answered

Every week on Open Thread, Vanessa will answer a reader’s fashion-related question, which you can send to her anytime via email or Twitter. Questions are edited and condensed.