There's a lingering social attitude, at least in my society, that it's expected for men to be somewhat promiscuous and fond of one-night stands, but if a woman shows more than a cursory interest in sex, she's a "slut", which is considered a Bad Thing.
The implication seems to be that she has low self-worth, and should be saving her sexuality as an asset to be used wisely; that she needs to work with the rest of femalekind to keep men starved of sex, thereby forming a supply cartel. Women who hand it out eagerly are, therefore, spoiling it for the rest of them who want to use sex as a form of power over men.
Sadly, it doesn't really work like that. Such manipulative bitches tend to end up lonely and miserable as they don't form proper loving relationships. And women who don't want to be like that still find themselves forced, due to social pressure, to disavow and feel guilty and dirty about their desire for sex.
I've met a few women in my time who have a healthy appetite for sex, and aren't ashamed of this. They don't go round propositioning everyone they see for sex... they are selective about who they fancy. It's just that they're enthusiastic about the idea of having sex with the guys and/or girls they like, and they're comfortable with that.
There is nothing wrong with this.
I've had lovey sex with slutty women. It's not seedy and impersonal; it's loving and passionate. We both want to have sex, and as soon as we both realise that, we do - enjoying it ourselves, and enjoying that the other person enjoys it too. We don't have to take advantage of one another in any way.
It's as simple as that!