I don't think women are more likely to be more eager or more invested in the sex being good in a relationship context. Actually when you have to live with a person every day I think women are a lot less likely to let loose like they would with a one and done hookup. And if deadbedrooms are anything to go by, often the security of a relationship does the opposite and makes a woman feel like she doesn't have to put any effort in, because the fish has already been reeled in.

I'm not saying that's okay or healthy, but relationships have as many factors that can destroy sex as they do factors that can enhance it. And that's me speaking as a monogamist who only wants sex in that context. Complacency is a real risk.