This is because women who are promiscuous are way more likely to divorce. They're also way less likely to have any successful long term relationships, or be happy and satisfied in a relationship. Let me explain why from a biological evolutionary point of view. Men evolved to want the most number of partners (1 man can have 100 kids in a year), women evolved to want the best partner (1 woman can generally have 1 kid a year). This is the great balance between passing on the best genes and propagating the species. Now lets go back to the "women want the best partner". Imagine a woman, lets say a perfectly average women 5/10, average in every way. How likely is it going to be that she could sleep with an above average guy? Maybe even an 8-9/10 guy, great genetics, gonna be very successful. Very likely, probably even several such level guys. But she's not going to get any of these guys to be in a real long term relationship, the guys are there for the sex, probably have been in this arrangement a hundred times. So eventually she is going to have to settle for an average guy on her level if she wants to have a long term relationship. Remembering and comparing this average guy to those former guys, because women are biologically programmed to seek the best partner they won't ever be happy or satisfied with what they're perceiving as a lesser partner. This is probably also why women initiate divorce 3/4 times in the united states. This isn't something that is cultural or taught, its universal and its subconscious. I find all this sort thing very interesting. Most of my knowledge I have on this topic comes from studies I've read and discussions I've had with a friend of mine who is a professor of anthropology. Another thing I'd consider is that women who tend to be more promiscuous generally have higher levels of testosterone, and there is also the issue of pair bonding.