Married women face a dilemma. It’s not that they want their husbands to cheat on them. But then again it’s not that they don’t want their husbands to cheat on them either.
Once married to a man, it is in the reproductive interest of the woman to monopolize access to all of his resources (material or otherwise) so that he would invest them in her joint children with him. Any sexual relationship he may have with other women might potentially jeopardize her exclusive access to his resources, so obviously it is in her interest to make sure that he does not have sexual relationships with other women.
The problem, however, is that, as I explain in a previous post, mating among all mammalian species (including humans) is a female choice; it happens whenever and with whomever the female wants, not whenever and with whomever the male wants. The more desirable a man is (the more resourceful, the higher his social status, the physically more attractive), the larger the number of other women who would want to have sex with him regardless of whether he is married, either in an attempt to steal him away from his current mate (mate poaching) or in an attempt to be impregnated by him so that their child will have his superior genes but then to turn around and pass off the child as their current long-term mates’ genetic offspring (cuckoldry).
All women have a vested reproductive interest to marry a man who is as desirable and attractive (physically and otherwise) as possible, but the more desirable and attractive the husband is, the greater the chances that other women would want him as well and thus the greater the chances that he would be unfaithful. There is a surefire way to guarantee that their husband will never cheat on them, and that is to marry the biggest loser that they can find so that nobody else would want him. But obviously no woman would want to do that.
There is an additional complication in the matter. Humans are naturally polygynous; humans have been mildly polygynous throughout evolutionary history. So it is natural for resourceful men of high status to mate with multiple women simultaneously. (But recall the dangers of naturalistic fallacy. Natural means neither good nor desirable. It just means is; it does not mean ought.) So polygyny – marriage of one man to more than one woman – is a deeply embedded part of male and female human nature. Men have always had multiple wives, and women have always been married to men who have had other wives.
It is true that, even under polygyny, many men still only have one wife while other men remain completely mateless. But we are disproportionately descended from polygynous men, because polygynous men invariably have more children than monogamous men. So most of us are descended from polygynous men (and, disproportionately, from highly successful polygynous men with a large number of wives), only a few of us are descended from monogamous men, and none of us are descended from mateless men. So polygyny remains a significant part of human nature.
Such is the dilemma faced by women, especially highly desirable women who are more likely to marry highly desirable men. The more desirable the woman is, the more desirable her husband is likely to be, and the more likely he is to cheat on her. The more likely her husband is to remain sexually faithful to her, the less desirable he is (and the greater the probability that perhaps she could have done much better than him).