Facepalm

I often wonder how much slut shaming has to do with women who expect/want this sort of behavior from men.

Honestly, probably a lot. Women are every bit as horny as men are in their late teens and 20s, but there's a ton of social pressure on women to be both virgins and whores; not have sex, but be sexually desirable. (Meanwhile, men mostly get told that they're supposed to be ready to go all the time.) The old Christmas song, "Baby It's Cold Outside" relies on this whole trope; she wants to say yes, but she can't just say yes; she needs to have some excuse. And he knows that, so he's trying to give her the excuse she wants. But to our ears now it ends up sounding very rape-y.