Broken

Remember that old Greek myth, about how there were once just humans, but then the gods split them apart into man and woman, and they become obsessed with trying to fit themselves back together?

Maybe that's actually a nice metaphor for sexuality overall, hetero- homo- auto- or what-have-you-sexual. Sexuality is in some way, an attempt to fix what is broken. That is why other peoples' sexual hang-ups can seem silly or pointless - because it's not something we ourselves lack. From our point of view, it seems like the other person is trying to fix something that isn't broken.