This will be interesting. As with many things, the motivations behind each individual's choices will vary; that one would never have occured to me but makes a lot of sense - for some, lol.
Me - well, I fall in "real" love rarely and very quickly, and out of such a love with difficulty - if ever. I often joke that if my 4 most serious exes of the last 14 years were of a different mindset, I would still have them all in my life and live happily if they could and would. Vi and Anne would be #'s 5 and 6 respectively, lol. And that's not including the "could have beens" that I missed out on because I've never been with someone as like minded and willing to work at a relationship as Violet until now. Strictly coincidentally - all of the aforementioned exes are bi, LOL. Funny, never thought about that before. Anyway...
Some people are wired for monogomy, some are wired for Polyamory, and some are wired for something else completely - or not at all. The trick is to find the person or people who are compatible with your wiring, and make it all it can be.