Most Helpful Guy
They just are. I can theorize as to why, and I think men actually 'settle' in relationships more easily than women do. But basically when the relationship is good, it's not that big a deal. On the other hand if the relationship is shaky, and he has a shot at hotter women, it weighs on him heavily.
Note that generally speaking when men cheat, they cheat with less, not more attractive partners than their main one.
Most Helpful Girl
This is exactly why I would be scared to ever be in a relationship. I don't want a dude to settle for me.