Its not like Hairstyles or Glamour are the only things coming out. There is 2 dungeons, a normal and EX trial, a 24 man raid, the MSQ, 2 side quest chains, and later on the revamped Diadem. Those are all content.
People care about how their character looks. People like having sweet looking mounts. People like collectable stuff. They are going to show these things off because there are players who are very interested in these things as rewards.