A lot of women have little interest in sex
I think this is a pernicious myth that helps keep heterosexual women having bad sex and the cycle continues.
I know when I was first sexually active, I was incredibly underwhelmed, yet boys were literally obsessed. You learn quite quickly (and so many cultural/societal messages reinforce) that sex is something men love and women put up with, but can use in a kind of gatekeeper style to have some lame kind of "power" over men. Hence all the "empowerfulising" shit.
My understanding was that sex was not optional in a relationship. If you didn't want sex (or enough sex) then they wouldn't want you. I did want all the other parts of a relationship, but I wasn't that fussed about sex because it was usually crap, had no idea at that point it could be good. But it's required for a relationship, so OK, whatever. I just assumed that was normal because men love sex and women put up with it.
Hormonal birth control also doesn't help. Lot of young women on hormonal birth control, because it's the most effective, especially the long term/no action required forms. But I only realised in my 30s this kills my libido (already not huge) stone dead, and I'm not the only one - it's a really common side effect.
Then many years having crap/boring/chore type sex and it doesn't make you want to try new things or have more or explore or whatever. In fact usually you dread this because "trying something new" revolves entirely around whatever new kink your bloke has picked up from porn (because "all men watch porn and it's normal"), and porn is invariably shit for women. And sometimes you've fallen into a trap of faking it/expressing pleasure so your man thinks that's just what sex with women is like and doesn't bother to try anything to make you like it more. Because men love sex and women put up with it. And you can't tell him that you've been faking it for ages because to insult a man's sexual prowess is the worst insult ever and would break the entire relationship (yes, all my previous relationships were this fragile!) Nor can you stop faking it because a fake orgasm is a nice easy "Stop now" that doesn't risk causing an argument.
The more women have bad sex the less they enjoy sex. The more men having sex with women who are used to bad sex means they don't think they have to make any effort, or what's the point in making effort, women don't like sex anyway. The cycle repeats again and again and eventually women in long term relationships just give up the pretence and poof, dead bedroom.
I hope it's changing, it doesn't have to be this way. I hope young women don't feel that they have to have sex to be in a relationship, I hope young men are interested and curious and want to know how to please their partner as well as themselves. I'm worried it's going the wrong way and getting worse, though, because of porn being so normalised. My generation was the first where boys expected you to be a porn star, but it's become more and more accessible and more and more extreme.