You have to bear in mind that our sexual brains have not evolved much since they were designed hundreds of thousands of years ago. The cost of sex for men is very low and very high for women.
Why? The female sexual brain (which frequently dominates their contemporary brains) knows that sex can lead to pregnancy which is very expensive; carrying the baby, risk of death at birth, lactation, and caring for the kid – especially if the man does a runner (hence why women are more choosey about men than vice versa).
For men, sex is cheap: they have millions of sperm and can deposit these at very low cost and quickly move onto the next opportunity. So the best male strategy for continuing your gene line is to have as much sex as possible with as many women as possible.
For a woman, the best strategy for continuing your gene line is to choose a strong guy who is likely to stick around. You’ll agree that these are not always in great supply.