Found this comment on reddit and for me it was enlightening:
Sure. They were told by media, parents, family and friends, that women would hate if they make it known that they want sex. They believe that pretending to not want sex is niceness. They believe that being direct, open, flirty and sexual is being an asshole.
In countless movies, the literal bad guy, the antagonist, is direct, flirty and sexual. The bad guy is shown to sleep around. The good guy isn't. He is "respectful". Not in the sense that he respects what the girl in the movie wants, oh no, there's tons on misogyny in movies. Not in the sense that the good guy doesn't want to sleep around, oh no, he wants to bang all the girls in his class. But he acts like a 'gentleman' and doesn't pursue that want openly, because he is a nice guy. The bad guy might even have the consent of the girls he gets (depending on the movie), but those relationships are still shown in a bad light just because the bad guy did it 'too fast' or somehow did it in a disrespectful way. The consent is often irrelevant to the morality shown in the movies. The promiscuity is.
Their literal definitions of right and wrong as based on appearances of sexual promiscuity, not actual respect and consent. So although I disagree with this entire way of thinking, that answers your question why they shame the women who put out on the first date, while at the same time wanting to have sex on the first date but pretending they don't. They get mad the woman they didn't play their part in the courtship of pretending to not want sex on the first date.
In reality, there's nothing disrespectful about wanting sex and making it known, as long as you leave people that don't want sex alone. If it's consensual, if they flirt back, if they make it known they want it too, it isn't being an asshole to sleep with them on the first date. It isn't disrespecting the woman to sleep with her early.
In reality, there's nothing nice about acting and pretending that you want to go on +5 dates before having sex. Nice Guys think this is the morally good act, the holding back of sexual urges is the right thing to do. They don't see this as dishonesty, because in their mind of course they want sex, they think it should be expected, that all men want sex. They are obsessed with sex and can't imagine a woman thinking they don't want sex. That's why they expect to be rewarded for hiding it. In their minds, the women know they want sex, and will appreciate the 'courtship ritual' of them acting like they don't want it. They truly believe that is how the dating game should play out.
In the end, they get mad the woman didn't fulfill her part of the game. They feel the woman was the one dishonest and manipulative, because she enjoyed the courtship "knowing" they wanted sex. If she wasn't interested in sex, she should have rejected their courtship.
I can tell you that in some parts of Portugal, Spain, Philippines, (I just noticed these are all Catholic, so probably similar things happen with some people in Italy, Latin America) that's literally how courtship goes. I can't speak for the US, I haven't lived there. In my experience of the culture from living there, and from talking with my family that are from these countries and talking with friends I made in these countries, the appearance of the woman being hard to get and the man not wanting sex at all but just wanting to give gifts and be a gentleman is actually really important - even if you are already banging. I have had sex with women who then in public would expect me to court them and they would "play hard to get" as if last night we didn't fuck. They would still put on a show of being 'difficult' to the public, to the families and friends, because they would be judged for being easy, and I would be judged if I openly flirted or showed sexual interest.
The conflict between that culture and 'american' dating culture is really apparent to me. The issue would go away if all slut shaming disappeared, but it hasn't and it won't.
Well yeah I'll give them the point that many "nice guys" are the same old assholes but with slightly better manners, and that they expect a reward for hiding their true intentions. Maybe they should indeed stop lying to themselves and others. However, it's very telling that the poster thinks women want courtship because they don't want to be slut shamed. Maybe it plays a small part in it, but women want to be shown respect, effort and care regardless of whether sex has been had. "She wants to be courted as if we didn't already fuck" ... Men think they need to stop making an effort as soon as they reached their goal, which was getting laid. She's already "used goods" so why make her the prize, right? The only one doing the slut shaming here is the poster himself. He thinks women who sleep with automatically lose value. That's a very typical scrote mindset. Because deep down they are insecure themselves, they think any woman who will agree to sleep with them must be low value. These men actually only respect women who play hard to get, at least for a little while. They created this problem themselves.