I dream very often of being someone else. No limits on sex, sexuality or age. Not too long ago I dreamt I was a young, bisexual man with bear-like proportions, though the sexual relations were an afterthought in a highly weird story about survival.
I am a middle aged woman, but shit it felt good in the morning to feel that strong.
Because humans are storytellers, not scientist by nature. Better (and not necessary for plebeians) story, bigger impact. For example religions or money have diminished our freedom-loving characteristics to almost none-existence, but they sure are good concepts to knit us together to form a society.