I use facebook to promote my bands gigs. It links up to the webpage. Plus i got back in touch with some old friends so that was sort of cool. But I could see where a lot of people just have no need for it. If your one of those i could care less about old friends, sharing pictures, liking bands/groups/pages etc to stay updated on their calendar etc etc.
I don't like how they manage the information flow on the site though. But you can turn off notifications to your email.