So, your script needs someone who will bang a lot of people. Given the prominence of the Male Gaze, odds are it's gonna be a girl who does a lot of dudes. But if you just have the girl who has no character beyond banging everyone in sight, then you might get accused of sexism. So, you have to come up with why this character is so sexually active. Well, what if she was raped? There we go! Obviously somebody did something bad to her, and it flipped a switch in her mind. Now you've got some psychological depth (even if you don't actually explore the issue in any well-rounded way), and your female character has an "excuse" for all her sex scenes. Or it could be a male character. We're not judging you... even if we really want to. Oddly, this troper can't recall many examples of this trope in material that's been "picked up"; he's seen it in a lot of formative works, so there's gotta be some foundation in "published" works that leads to the idea. The closest he can recall is how, on Loveline, Dr. Drew has a tendency to ask promiscuous/kinky girls if they were victims of sexual abuse.
Hello, Unknown Troper. You'll need to get known to lend a hand here.