Its the same with any new fad - the kind of girls who start the fashion off manage to carry it off and look OK but then the great unwashed masses get hold of them a few months later and wear them with wholly inappropiate clothing.
Take the leggings craze as an example. When they were first in fashion (about 18 months ago) the laies who were wearing them at first looked rather fetching and i thought it was a nice way to show off some leg without actually showing them off (If you get my drift!). They would be matched nicely with a nice flowing, but fitted short dress.
Roll on a few months and every lumpy middle-aged woman is wandering around with them on and looking absolutely hideous and cringeworthy.
I even saw a 40 year-old yesterday wearing those stupid Ugg boots with a pair of black leggings on with a 'normal' shirt on top. Everyone was looking at her walking down the road stifling a giggle as she looked ridiculous.