Is it really so difficult?

Tweet

I was driving home after work in some traffic today. As there were many people making the trek home, I noticed something rude happening a few cars infront of me. The cars going straight were either blocking the road where people were waiting to turn from or sped up so they couldn't go. Please keep in mind that they wanted to go the same way we were all going. So being that I'm the nice guy and nobody was going anywhere fast, I let three people go along the way. The first waved to me to thank me but the second and third thought it was too much trouble to give a kind gesture towards me. So my question stands, why is it so difficult to be a little courteous towards someone that did something nice to you? Is it too much trouble to give a small wave? This is the reason why people don't want to do nice things. How does everyone else feel about this?