Monogamy is common in the wild, but life long monogamy is not. It's a survival mechanism for protecting young. Believe or not, in most species, the female is the promiscuous one. For many years it was believed that the male was (in nature), because it fit with the male domininant norms/traditional thinking. In the wild, a female can benifit her fitness the most when she is socialy monogamous, but sexualy promiscuous, therefor secret sex lives take place with many species. Multiple partners aid sperm compitition and promote genetic diversity, while monogomy aids the purpose of rearing young. There was a study with ducks where the more males she porked, the more eggs there would be in the clutch. This has been noted in many other species too. In our close relatives, the chimps and bonobos, sex is practicaly a form of social bonding. But then again, gorilla males have harems and will sometimes kill babies to win over a mate.

I think being pussy whipped is just a survival mechanism.

Praying Mantis females will rip the head off of the male and eat it during copulation. When it is done, it will finish him.