Organisms that enjoy sex reproduce more.

Organisms that enjoy having sex until genetic material is exchanged reproduce even more.

In mammals where reproduction can decrease fitness of the females (being pregnant means worse hunting, or worse at evading predators, and more needed calories) the females tend to be selective. There is an evolutionary pressure for them not to attempt to reproduce with every male they see. If they did, they would likely cut their own life short and the offspring may not make it.

So their orgasms become more elusive, and often include outside factors than the physical actions as well. For them the evolutionary pressure isn’t just to have sex, it’s to have sex with someone who could keep them alive during pregnancy, childbirth, and until the offspring are self sufficient. Not just capable of that, but willing. That’s the whole “emotional connection” thing, and why most women aren’t just hung up on looks.

But to clarify this is something way older than humans. Because orgasms have been around a lot longer than we have. Humans just have the language to d scribe the behavior it doesn’t always mean we understand our own.