I dunno, I don't really follow fads, but I do understand them. Malcom Gladwell's book 'The Tipping Point' explains the logic of them pretty well. It's a really good book.
There's also the status and wealth display stuff, i.e. 'I can afford to buy totally new clothes each month, to stay in fashion'. Wealth display has always been a big factor with fashion. That's why in the past, fat voluptious women were considered attractive, since only those who were wealthy could afford to sit on their ass all day eating to get that way; but now slender is attractive, since only the rich can afford the plastic surgery or the time to spend hours in in a gym with a personal trainer. Of course, people who aren't rich also try to get that super body, but the reason it's considered attractive is because that's how rich people look.
It really doesn't matter in the long run. In high school it's a big deal, but afterward people don't care as much, at least in my experience.