I used to snigger when I’d come upon Vogue’s lazy-seeming reasoning behind a trend: “It feels right, right now” or “It feels fresh.” But after reading Eric Wilson’s so-called investigative story in The New York Times about the arrival of the round glasses trend, I now realize that Vogue is onto a pretty basic truth about why we like what we like — sometimes, we just do, if for no other reason than we crave change. Because no matter how much so-called evidence one turns up about why so many designers fall for a certain style, as Wilson does, and why we all follow it, any reasoning for something so subjective seems contrived. Besides, as Wilson points out, the last time round shades were hot was in 1989 — and as every experienced style observer knows, two decades represents the life cycle of nearly every trend, from music to makeup to sunglasses.