Why do women cheat? Because they can.
Because she will not experience censure and shunning from her friends, who will blame the husband for being inadequate to her needs, and thus justify her cheating.
And in a divorce, they walk away with half, alimony, child support, etc. Not surprising fewer and fewer men want to get married.
Just in normal romance, things change on a daily basis. One day it takes 20 minutes to get her warmed up. The next 2 hours. The day after, she's jumping on you, getting you going.
Then of course there is the getting going and she hits the brakes.
It's like trying to open a safe and changing the combination everyday.
Throw PMS in there and it's a crap shoot for the man to get anything right.