I’m with Tim Gunn on this one (and really in a sense anthropologists and sociologists before him, like Erving Goffman), fashion is a form of rhetoric. What you put on tends to communicate, be your desire to align yourself with your favorite sports team or with a musical subculture, advertise your competence for a job or political office, or make clear that you are available to the opposite sex (or maybe just for sex). What we put on is emblematic. Even the slob who just throws on whatever is in his closet this morning is inadvertently telling us something.
Thus, as games have grown more mature and more interested in communicating messages, stories, and ideas in a more complex way, it seems to me inevitable that the virtual closets of our avatars have expanded. In a medium where the visual plays a big role in speaking to its audience, understanding characters through their physical appearance is important. Character customization additionally plays to the medium’s strengths as it allows the player the opportunity to participate in how a story is told and how their virtual self is supposed to be understood in the context of the virtual performance that they are taking part in.