Women are the ones who decide if sex happens. Men are the hunters, we're trying to get it from whoever. Women don't need to be especially attractive for a guy to have sex with her, but for a man to be desired by multiple women, he has to be attractive in some way.
So if sex happens, we got what we set out for, it's an accomplishment. And the woman allowed it. So if the same guy gets it over and over from different women, he is accomplished and attractive. If the same woman allows it over and over with different men, all it says is that she has low levels of self-control and possibly self-esteem.
It's a "double standard" yes but it takes effort, skill, charisma, as well as some level of good looks for most men to get sex, whereas most women can have sex any night she wants, if she is willing to put out. So I don't wanna hear bytching about a double standard because we all want sex, some of us just have to work harder for it.