I used to be a 'nice gal'. That's how I know they exist.
I've known many women too who would attest to having been nice gals, especially in teen to mid-20's. It's the 'nice gal' zone. Yikes.
When I say men who treat them like **** and are off to their next big conquest, I don't mean just sex, though sex is often a part of it. But I'm certainly not one of those people who think women are being taken advantage of just cuz they are having sex with someone who isn't committed to them forever. I believe women ought to (and many do) enjoy the sex just as much as the men do, even when it's a one night stand. But yeah, there's more to jerks than just having sex and leaving.........