I so don't do fashion, what's the point, really. Regular jeans here 5 bucks, "fashion" jeans 39.95, just so you can have the privilege of having them come pre-torn, um no thanks.
Seriously though, the some people care about the trends, I think, because they worry more about what other people think of them that what actually matters, who they are as a person. So they run with the crowd and buy or misuse what ever is currently "hot". Oddly all those "out" clothes I have kept for so long because I just like them(my old Duster jacket, waterproof and functional, for example) are actually starting to be in fashion LOL go figure! These things run in cycles too! Torn jeans were popular in the 80's, mini skirts in the 50's and 60's, ect.