Asking why women cheat is just as useless as asking why men cheat. No matter what answer one gives, it all comes back to being selfish and thinking of oneself moreso than the person you're in a relationship with. Once in that space, the relationship is just a happenstance. Cheating is always a choice-never an obligation. Instead of making the choice to cheat, a woman could always make the choice to stay at home instead of going out. She could make the choice to not give out her phone number to another dude in the first place. She could make the choice to not put herself in the position to be propositioned in the first place.
However, if I were to give a reason why I think women cheat, I would say mostly revenge. If a woman cheats out of boredom, then she's not a woman...maybe just a b#tch. But a woman does not cheat because the sex with her dude isn't mind blowing every time they hop in bed because a woman doesn't live vicariously through her own vagina. And she also knows that sex is one part of a relationship and not a metric for the relationship. But since, we have more hoes than housewives in the world, I'm not surprised that some have mentioned "boredom."
Lastly, I must say I find it funny how dudes really think its their d#ck that keeps a woman faithful...on some "she cheats cuz her dude aint hittin it right...never happened to me tho."
Dudes really think they're the only one who gave their chick a good feeling? Dudes really think that there's not another dude who's even better in bed? And guess what? That dude probably still got/gets cheated on at some point too. Its not about f#cking a woman's vagina...its about f#cking her mind. That's how a woman stays focused on you.
Dudes doing olympics in the bedroom and can't even get their chick to make them a sandwich without a five nut orgasm

...oh, and she still paid her ex boyfriend's phone and cable bill after all that good sex.
Peace