What the difference is between hypergamy and general shittyness.

Most of the responses I've seen are that women will cheat on you, but I have seen very little evidence that it's because of hypergamy.

From what I can gather, given the right circumstances, both men and women will cheat on their spouse. For some reason, we've decided to give it a name when women do it and we call it hypergamy. When men do it, it's because... well, I still don't know.

First, let me make sure I understand the concept of hypergamy. This is the idea that women are more attracted to a man whose social class is higher than hers. Social class is culture specific, and in our culture, it's a handsome man that's older, with a good paying job and a great deal of confidence.

If I have that correct, then what I don't understand is when hot nurses are fucking the orderly at the rest home, or an old high school heart throb that connected with her on Facebook and they hook up. How can these be considered hypergamy? They probably aren't moving up in social class. It's simply a case of a really attractive guy giving her tingles. Which is really no different than a sexy 22 year old girl giving a man the tingles.

Can someone help me to understand what I'm missing here?