He gets what he wants, when he wants it from whomever he wants it from. You get the dregs and, worse, could also be having your life and health threatened by his philandering. Not a good trade-off in my book. I see that as a lame excuse that many use to excuse their cowardly, hurtful and inexcusable behavior. If he was a man, he'd leave and stop all pretense of being married.
Marriage is, among other things, about total inclusion and absolute fidelity.
If that's not how it is, it has no business being called a marriage. It's a sham. It certainly isn't love. When youlove someone you will do everything in your power to avoid bringing them hurt, disappointment and dismay. I was in a 25-year abusive and ultimately unfulfilling marriage.