... because I am just a multiperson person.
... because my partner pushes me into it (constructive dismissal).
... because of strategic reasons.
Hm. You mean like if your wife/GF cuts you off? Or seems to go out of her way to emotionally alienate you.
Yeah, that does happen. Often it is done BECAUSE the manipulating person is cheating and wants to push you away, or force you to cheat too so you share their guilt. I've seen it done... and I think it is usually not a conscious thing, unless it is someone wanting an excuse to divorce and hoping a reason will help them get more in the split maybe.
Fiddling While Rome Burns
Carthago Delenda Est
"I used to roll the dice; see the fear in my enemies' eyes... listen as the crowd would sing, 'now the old king is dead, Long Live the King.'.."
Now, that being said, if you're a serious player then none of that matters and if your game is good enough you'll get your three way. If you're rock solid then you should also be able to parlay that into going totally live.
Other than "none" or "other," the list of the poll is a pretty good one.
I never had a "relationship" prior to my wife and she never so much as had a BF. I'm not sure "cheating" as the OP means it exactly applies to our relationship/marriage, but I cannot imagine my ever cheating on or betraying her in any way under any circumstance. Nor do I ever think there would be any reason to. If I ever wanted someone else I would talk it over with her, and visa versa.
Cheating would seem to involve lying and deception in relation to sex (I assume that is what the OP means by "cheating") or otherwise secretly establishing a relationship with someone else. We both began from the first first talk we ever had with perfect candor about each ourselves - I at least never thinking a relationship or anything else even a prospect with her. That level of truthfulness just became how our relationship and then marriage works. Sex is a definite part of this, but we had moved across country together and owned a house together before marriage or sex. It wasn't that we had become perfect friends as much as extreme curious infatuation with how different we were from each other - yet some oddities about us both that seemed to make the exactly wrong couple exactly right.
I don't know how to put it but sex just for sex maybe is a big deal to people, but isn't to me. Sex just for sex is cheap, easy and even came to not be worth the effort. That's maybe why I don't understand "cheating" on a sexual level. "Emotional cheating" on someone - meaning you are still pretending to be something your are not to your spouse/BF/GFr is something else and that's rotten in my opinion.
Not relative to my situation, but I can see circumstances where someone would want to find the replacement first - like finding a new job before quitting the old one. One such reason could be economic. I'm not advocating or justifying anything, but I could see a woman with children and an economic and maybe alcoholic/druggie lazyass loser husband grabbing onto a man who seems solid and financially secure - but not leaving the one home until locking down a superior replacement.
Ideally and rightly, the person would call it off first, but calling it off when there is a house, kids, married financially at the hip etc that isn't maybe always as simple as it sounds.