Yeah, my Sims don't cheat unless I need it for a storyline. (I had a family with an evil and noncomittal wife married to a family-oriented man, they have a teen and she had a baby with someone else and he divorced her and kept the baby.) I don't like cheating; usually if my Sims fall in love as teens they stay together forever! I've been playing since 2017 and have had two divorces. (The other one was just a couple that ended up being poorly matched--she was outgoing and had a huge family that came over constantly and he was a loner that was perpetually tense from seeing his wife's family.)
I don't mind a polyamorous relationship where everyone is on the same page and agrees to the arrangement (and have played that!), but I don't like nonconsensual sneaking around. (I played the Leverage team with Parker/Eliot/Hardison as a committed triad and Nate and Sophie happily married.)
And I think calling up your romantic partner and saying, "Hi, I think so-and-so is cute, should I ask them out?" is obnoxious behavior that should get someone dumped. I mean, if you're not officially dating maybe they're being manipulative and trying to get you to say, "No, I think you should be with me!" but... why not just ask to be boyfriend/girlfriend/partner instead?
That said, I've also seen a YouTuber say, "Tee hee, the Sims 4 is a game about infidelity! we all do it! let's go break up some townie marriages hahaha!" so I do understand that my play style isn't everyone else's play style. No judgment, it's all how you like to play.
That said, yeah, I'm sure it's hard to accommodate both play styles. I've suggested a drama slider before, which is mostly a joke because I don't know how they'd implement that technically, but... yeah.