People who pretend not to hear?

I had a fella get on the bus (coach) the other day with a can of diet coke. As I'm tired of people leaving their rubbish after them, I said "just be careful with the can that's all". Expecting to answer "yeah, no bother" I looked back down at the cash I was counting. But there was no response out of him, so I looked up again and tried to make eye contact with him, and only then he replied "yeah yeah yeah", while seeming a bit irritated. He was hoping that I'd just say to myself "Christ I'll be all day loading these passengers with this so I'll just leave it go". But only when he knew I wasn't going to let it go did he finally reply. But given that he tested, a few seconds after this (having not printed his ticket) I stopped counting out the change, and said "actually, do you know what, if you're coming on bin the can (pointing out to the bin) and join the back of the queue". He rolled his eyes and went out to bin it. In his mind I was somehow cheeky to even make the initial remark. By the way he was acting I was 90% sure he'd have left it on after him.

I get something similar to this sometimes with passengers (mainly young ones) on city routes (where there's two rates) who won't say where they're going leaving me wondering how much should I charge them. Often I can tell where passengers are most likely going based on what part of the route the bus is on, and other things. Mostly I don't need to ask, but when I do ask a lot of them just don't answer. Now sometimes this might be because they don't hear, or that they're just being stupid, but often they just couldn't be bothered answering. Sometimes I just say to myself "right, higher rate it is then". But lately I'm more insistent on getting an answer. I want to know if they're being rude or not.

Ever get anything like this? It's like a mixed combination of shyness and contempt... mainly the latter because I don't believe anyone is that shy really. Do they know that if they look at something far away that it'll seem as if they look so out of it the the other person won't even go to the bother of re-asking? Where do they learn this.