(NSFW) How often do you realize you had sex (any kind of it) because it was expected from you not because you wanted it?

I was disturbed with the realization that I was having sex without wanting it. That sex was for different reasons than for my pleasure. I allowed to use my body consciously or giving oral pleasure to a partner, thinking this is the way it is, this is what is expected, I’m doing it right.
Then I talked with my female friends and they admitted they are having sex quite often no matter if they want it or not.
I start thinking where is this coming from?

Is this the culture thing, where females are raised for submissive role and therefore they submit more to the expectations? What about men? I don’t have a male friend who admits he had sex unwillingly.

Humans, I need your honest opinions and experiences in order to understand this unfair phenomenon where people themselves unconsciously create the unfairness by participating.
Thank you :)