In high school, why is the theater,band, or other type of arts students considered outcasts?

I was sort of into the arts in high school and I noticed a lot of the girls and guys even in the theatre cles and club felt outcasted by everyone else. Heck even I was told by one of the really weird ones, I'm an outcasts and since I was an in-betweener, misfit myself a couple of them sometimes saw me as an outcast (but that was after I bitched about one of the major theater/popular geeks (the popular one in the group, who was super fat and gay(after high school)) ually harred me and was a really mean, insecure guy. But anyway, why are artsy people considered outcasts in high schools normally?