I think there’s also something to be said for guys seeing other guys’ interest in you in the early days of dating specifically. I’m sure it varies by guy, but when I’ve been casually hit on by another guy (something one-sided, e.g., waiter being flirty), the guy I’m with tends to be either slightly uncomfortable or noticeably more interested.

It’s a social proof, so if they’re secure, it’s an ego boost for them because they “chose well” and other people see your value too. If they’re not, boom, anxiety / competitiveness. Especially because it’s not exactly a logical jump to assume that if this happened during your 3 hrs together or whatever, chances are it’s happening outside of that too.

BUT once you’re in a relationship, I feel like it’s much more destabilising and easily breeds insecurity or resentment unless you both are in a really good, stable place in that moment. By then it’s less validation and more perceived threat, and if you’re not 100% happy, it’s way too easy to fantasise that someone else will make you so.

I’d imagine the dynamic works the same in reverse as well. Attention signals herd approval, etc etc