There are other reasons bf and wife are still together. I'm trying to be vague(ish) so no one knows who I am....
Mostly, the cheating in their marriage has been one time things. And why they are still married comes down to finances. Today, anyway. Before that, I think it was a sense of loyalty, the kids, etc. And of course he's NOT being loyal by having an affair, but I don't think she cares (as much) as long as he comes home to her every night.
I wasn't looking for a married man, or an affair. I wasn't even looking, but I was unhappy in my marriage. Same old story. He is also NOT a co-worker or former high school flame as so many are.
My doctor only recently suggested bipolar as a diagnosis - after I mentioned the sex things. She can't say with certainty, of course. It does seem to explain phases of my life, even if it doesn't excuse them. I certainly am not one to throw a mental disorder at every misbehavior and call it good. I'm skeptical. I have found, though, that if I'm aware of what might be happening with my thoughts, that perhaps I can preempt, or channel any harmful actions.
Back to plural marriage for a minute - it would legitimize polyamory and negate the "need" for most affairs, I believe. But that is probably discussed in the Religion thread. I certainly didn't mean to get this deep in my introductory thread. It's alright with me - but I don't know how the mods feel.
Dan Savage's book sounds good, too.