This trope does have some basis in real life. The idea of the All Girls Want Bad Boys and the Forbidden Fruit tropes play a part.
Because the possibility of a woman being abused is worse than a man being abused
It's quite rare for a female hero to have feelings for, or pursue romance with a male villain, despite things such as the
All Girls Want Bad Boys trope. There are several possible reasons why it's often male hero/female villain and not female hero/male villain. In most societies since antiquity, there are various levels of social codes, both spoken and unspoken, that dictate that men should protect women. This could mean that with the hero/villainess dynamic, the hero is there to protect the woman from herself. In a heroine/villain relationship, a woman who would take up the mantle of heroine is unlikely to be one that would seek (and would be reluctant to accept) protection, not to mention that a villain is unlikely to offer protection. Additionally with a male villain, often
he would be a threat, in a way that's indicative of an abusive boyfriend. In the real world, domestic abuse is something both men and women experience, but statistically men abuse women more often than vice versa.
Because men are easier to seduce than women
There is also the idea that a heroic woman would have the moral fiber to refuse the advances of a villainous man. This carries the
Double Standard that a woman can resist her libido if the man is evil, but a man
can't deny their libidos even when they should. Some people think that
Women Are Wiser, and thus heroines will know to resist the villain's charms and do so. The existence of the
All Girls Want Bad Boys trope proves this isn't universally true. Some think that men aren't as good at seduction as women. This stems from the fact that men and women are usually attracted to different things in each other—men are more attracted to physical appearance, which allows for faster seduction.
Because writers are biased
It could at times be, for example,
male writers idealizing their female characters out of
Author Appeal, or
feminist writers seeking to put out a positive image of women.
Because heroes can be trusted
Another reason this dynamic is far more common with male heroes and female villainesses vs. heroines and male villains is the morality of the man in question. As a hero, the audience almost never needs worry that they will be abusive, emotionally or physically, to the woman in the equation. Whereas a villain may or may not have a code of morality, or at the very least might have it be left ambiguous and thus, worrisome. A villain with an eye on the heroine might come off as obsessed, stalkerish, or worrisome about their intentions because of their ill morality as a villain. If they don't care about harming others, what's to stop them from secretly conspiring to harm the heroine?
