Not just Star Trek XI - the new Sherlock Holmes movie isn't even on DVD and there're a zillion Holmes/Watson vids. I'm not into Harry Potter but I think there are probably many slash vids in that fandom (more than one movie, so more source, I guess) - and I'd assume (also not my fandom) LOTR, as well? I don't know if it's about availability of footage exactly (that rarely stops anyone) but movies generally don't have active fandoms the way TV shows do, except in specific instances (like Sherlock Holmes, Star Trek, LOTR, and Harry Potter) - and that might also explain difference. Not the footage, but the fandom.