I used to fake orgasms when I was younger. Part of it, for me, was just not having enough self-respect or agency to realize that my experience mattered. I only faked when the sex wasn't fun for me, which was pretty often because I didn't feel like I was allowed to give any constructive criticism or ask for what I wanted (I'd read too many novels with male protagonists in which sex was a thing he does to her, and she's either good and yielding or she's nothing; and she certainly never has opinions or preferences). It genuinely didn't occur to me until I was maybe 24 that I was a person, and one half of the people involved, and was allowed to want things and even sometimes maybe to get what I wanted. So my goal in sex was to get him off, and when sex was boring or uncomfortable, I wanted that to happen faster. Faking enthusiasm and faking orgasm made it over sooner.
I think faking orgasms is a phenomenon born of two things. 1) cultural attitudes toward sex that obscure or repress women's sexual agency, and 2) lack of communication about sex between the partners.