Is it Hard to Be Friendly?

Yesterday, while I was taking my daughter into school, we were stuck in traffic. As we passed the school buses also stuck in traffic, my daughter and I started waving at the other school children looking out. At first, a pair of girls sitting next to each other waved back. Soon, half of the bus were waving at us and smiling.

I wonder why this doesn't happen more often. I also wonder why this phenomenon doesn't happen more often with adults. On the bus, walking down the street, people seem to avoid eye contact, let alone smiling. Where is the fear? How hard is it to overcome this fear? Here's an inspirational video that a friend of mine sent me http://www.ithou.org/node/671.