'I think this was one of those times where you go along with it because you can't be arsed' and from another 'yes, we've all been in situations where you can't be bothered but think "whatever"'
What is it you think that they can't be arsed doing? It's put up the resistance required! Of course they don't want to see it as a threat, but here's what's going through their head:
If I say no, then he'll go on and on, asking, pushing, whining, he'll get angry and flounce, probably go and make up stuff to his mates. I just want to be asleep, I don't want to spend half an hour justifying why I don't want to have sex with him, so it'll be quicker if I just have sex with him.
Since you're happy with the mugger, we'll keep running with that. It's not a mugger any more though, it's a beggar, one of those ones who just won't take no for an answer, and they're next to you, in a room that you're trying to sleep in, and you just want to go to sleep but he keeps asking for a tenner. Do you give him the tenner? Of course you bloody do. And is that beggar certainly guilty of extorting that money? Of course he is.
Same thing. But instead of money, it's putting a penis into a person.