I struggle with the same thing. I was raised in a different country with different culture values, and it was just a given that folks gave you a nod or thank you when you were nice or paid them a good turn.
I now subscribe to Dawn's approach - I'm nice because it makes me feel like a nice person. It's great if my kindness is infectous to another, but if not, oh well, their mood isn't mine to control. Before, I found myself annoyed far too much and I'd gripe to my spouse about other's lack of kindness acknowledgement, which didn't make me feel like a good person. So, I stopped.