> Except that almost nobody who hits a kid on the highway did it on purpose, and everyone who commits sexual assualt does it entirely on purpose.
Counterexample: There was a recent episode of Vice titled Consent, which included a mediation between a man and a woman where the man had no conception that the woman hadn't consented.
It's not hard to see why this is common. When you have a power dynamic, even subtle and unofficial ones, someone who doesn't want to consent has an internal conflict. They neither want to participate nor want to harm their relationship with the other person.
Those types of situations are horrifying. If you signal refusal using overtly transparent methods (throw a drink in their face, scream, slap them), they'll get the message but at the cost of making a scene and potentially souring the relationship. If you try to be too subtle they won't get the hint. The middle ground exists, but with pressure on both sides, it's not the least bit surprising that sometimes someone errs too far on the side of not making a scene. I don't mean to blame the victim in a moral sense, but in a technical sense where sometimes the situation is hard and the right balance isn't clear.
In many of these cases it's still fair to blame the other person for not getting the message, but the failure can certainly be in perception rather than intent. In a sense it is very similar to when you hit a kid in the road because you weren't paying enough attention.