I joined here because the forum had fanfiction, more importantly, POKEMON fanfiction and since I was into it at the time I joined. Same reason I joined SPPF. These two are really the only forums I joined that I stayed active on, i've joined others mainly because my friends made them and I was lending support, and stuff like that.
it's just nice to have a place where you can discuss your interests with other people who share them, especially when not all your irl friends are interested in them. and even though my love of pokemon fanfiction is long gone, I still like killing time by reading posts, meeting new people, and lurking in other newer sections that interest me more now (for example, video gaming and books/music/movies) :)