boys aside.
When men do it, it's different. They are jerks. Also they don't like or want one person, they want multiple people. Anyone that looks nice, anyone that would screw them. I have meant absolutley nothing to any straight guys that I thought I did.
I just can't be bothered dealing with them.
Sounds like you've just had the misfortune of being predated on by assholes. I know 4 female friends off the top of my head who're absolutely adored by their male partners, and I very much loved my ex and never had any desire to cheat on her while I was with her. I've also had a fair number of casual sexual encounters where neither of us meant anything to the other, or even knew the other very well (which, incidentally, were all pretty shit and unsatisfying compared to being with someone I cared about), but it was always mutually understood that that was the case, and I've never decieved a girl into thinking I cared for her when I didn't.
How have you ended up with these guys?