I think most people are aware that men can be insecure about their significant others going to clubs, bars, or parties or on girls' trips. We know that our girl is likely going to be approached and hit on by numerous men, and we also know, generally, that we can't demand that she just completely ignore them or immediately tell them to f off (because that is embarassing unless the dude is being overtly rude or creepy). Often, if we do make these kinds of demands or requests, she will be offended and accuse us of not trusting her (which may or may not be the case, depending on the individual). So, we have to make peace with the fact that she is going to get this kind of attention and, at least some of the time, she will get a sense of validation from it (it feels good when someone flirts with you, so long as you don't find them repulsive for some reason).

However, men do not get approached in these situations anywhere near as much as women do. We have to do the approaching most of the time, and most women, i feel, would have a much bigger problem with their men proactively seeking out the same kind of attention and validation that they often get by just existing at a club, bar etc and looking decent. Imo, women in general would not make peace with the idea that their man might go out and look for opportunities to flirt, even if they completely trust him not to take things too far (whatever that might mean for that couple; couples do have different rules and boundaries, after all).

So, attached men should be able to approach women and flirt with them if their s.o.'s enjoy the experience I'm talking about. That's the only way we can acheive the same kind of validation.