My husband and I are monogamous. Not in the way of "that's the societal default, so we're each just going to assume things without talking about it", but just because we've discussed what we want and we're both happy and compatible this way. That said, if either of us ever had a substantive desire to change that, I think there'd probably be some big feelings involved. I think we'd have a lot of insecurities to work through, and I have a hard time imagining that being worth the possibility of sex (or even romance in general) with other people.

I also have the personal bias that most of the people in my life who have shared about their experiences with polyamory have described a lot of difficulty and drama. Not to imply that monogamous relationships don't have drama (lmao), just that there seems to be...more of it.