Succibi and incubi get a bad wrap. Sure, they feed on the energy that comes with pleasure, but that's not hurting anybody—quite the opposite, really. But some jealous lover kills a bedmate in a fit of pique one time, and just because a succubus happened to be there, now it's all "draining essence" and "stealing souls." What are they gonna do with souls, anyway? Taking care of a soul is a lot of work! And why kill your meal when you could go back for seconds later?
Most demons don't bother with the human realm—there's plenty of sex to be had in the demon realm, after all. Sometimes, though, one might come exploring if they're feeling adventurous or looking for something exotic. And the people they meet never seem to mind...