In most cultures, men are reluctant to commit to sluts.
Why? Because a slut has little self-control.
To understand that, you need to understand a key difference between the sexes.
Take your average fertile male and female. The female has no issue getting sex. In fact, on that front, most of her time is spent refusing sex, while seeking commitment. The male, on the other hand, must prove he is worthy of sex.
So why would a female give away sex without commitment?
Because she was unable to control herself and her emotions.