One of the primary purposes of fashion is to instill anonymity within the cultures that perpetuate or expand on said models of understanding the universe (previous blog). If we feel comfortable within a specific community of fellow thinkers, the last thing we want is to appear as if we stand out or disagree with them. Therefore, when we admire an ideal someone else represents, we pull the most banal and primary things (usually physical appearance) from that experience and seek to replicate it.
Before the advent of the internet, it's easy to see the usefulness of this behavior.
However, given the incredible rate of information exchange we're subjected to on a daily basis, fashion is rendered useless. You could even speculate that the less any given community receives and exchanges information, the more fashion becomes an increasing necessity to establish rank and compliance- and conversely- the more information a community receives and exchanges, the less it has to rely on fashion-expression.

A creation in its truest form serves as a critique of all previous creations, and more locally (music/film/etc), serves as the pedestal for competitive growth. In effect, when we write a song, it is a commentary on all the songs we've ever heard before, and to an even greater extent, on a more primal level, every sound we make is in reaction to all previous sounds we've heard. We then- as consumers- base our taste in music and sounds on how relevant the said musician's critique of former musics is to our own critique. We are, after all addicted to our own models of the universe, so it's only natural that we'd be obliged to serve those models with similar or more complex versions of the same model. Genres seem to be the best way to describe this phenomenon.