Answer: first and foremost, he wants a reliable source of sexual tension relief. He may vaguely want more. We can safely group all of that under the term "very little".
What does a woman want?
Answer: Since women are fantastically good at lying to themselves about they really want -- they really believe their own delusions -- they will never admit that what they actually want, is essentially: financial tension relief. She may want more. We can safely call that "very little".
So, now we have a recurring tit-for-tat business. If you keep giving me what I want, I will keep giving you what you want.
This business is actually quite important, because as a -- sometimes even unwanted -- side effect, we end up reproducing.
When does the protocol fail?
When the woman does not experience financial tension, because she is from a wealthy background or because she makes ample money by herself, the only thing that she is getting out of the arrangement, is the aforementioned "very little".
Of course, initial infatuation, as well as biochemical pair bonding ("love") will in vain try to keep things together. It will work until it doesn't anymore.
High levels of income in a geographical area, devalue what the man brings to the table without devaluing what the woman brings. Thetefore, the easier that the money is to get by, the higher the divorce rate, obviously mostly initiated by women.
Once you understand this principle, the optimal strategy for a man is rather simple: Make sure to make good money, and then move to an area where there is almost no money. Instead of you queueing, "It is not your girl, it is just your turn", it is the girls who will be queueing.
From personal experience, I can testify that the game-theoretical results for this strategy are incredibly stable. The equilibrium result never include the woman cutting herself off from the money you give her or renouncing access to financial tension relief.
Is she happy? Well, since her happiness is the result of staunchly believing in her own delusions, yes she is happy, because a woman is happy when she systematically lies to herself that she is.