Hey, you, pick up that piece of garbage!
Huh? Me?
Yeah, you. I just saw you throw a piece of garbage on the ground. Can't you read the No Littering sign? It's a $ 500 penalty for littering, so go pick it up and put it in the garbage can over there.
Why should I do that? It's only a piece of garbage. Why should you care?
Because this is a public place, and I want to spend my time here without having to look at your garbage.
Listen, I really don't know why you're making this into such a big issue. It's only a small piece of garbage in a large space. It's not like there's garbage everywhere. Besides, someone will come along to clean it up at some time or another.
It's not the cleaner's responsibility to pick up after lazy people. It's part of your responsibility to make sure that the place is neat for other people. If everyone thought like you, there'd be garbage everywhere! The cleaners can't be everywhere!
Ok, whatever. See, I'm putting it in the garbage can.