>>50540
Because there aren't severe enough consequences for being disloyal. That's not even just with romantic relationships but any relationships in general. Don't waste my time and make me regret even being with you in the first place. I don't want to be with you only for you to show me I'm not worth being the only one you mate with, basically. That's essentially letting other mates enter you tribe to have a go at her.
If you need the sex and attention so bad from other men, don't even get with me in the first place.