Evolution. A single woman can get impregnated by a single man (except for the few cases of fraternal twins with two different fathers) while a single man can impregnate thousands of women.
There are two basic survival strategies for the genes passed on my men:
1) Promiscuity assuming a few kids raised by the mothers will reach sexual maturity themselves
2) Monogamy with all kids being raised by the mother and father and almost all will reach sexual maturity
Interestingly the second strategy proved to be far more effective!
Many men following the first strategy are narcissistic and their true intent is typically self serving. Their goal is to accumulate more of two things: power and money.