Fashion is a temperamental, unexplainable beast. It's quite the phenomenon to think that people will dress in the same style without an explicit agreement.
Take for example the flappers of the '20s or the disco, glam rock era of the '70s or whatever the hell they were thinking in the '80s.
The unspoken group assent to style is inexplicable as far as trying to find its source. All we can do is observe the aftereffects. In regard to this fall fashion season, here are a few of the things that we've all somehow implicitly agreed to.