I read somewhere that the difference between humans and great apes is the ability to put ourselves in another person's position ... to see things the way they see them. It's a higher social capacity. And unfortunately, I think it isn't really all that universal among humans.

So I have a different theory. Human tribalism. We respect and will share with people "in our tribe" ... people who are like us. In the road context, that means people who use the road more or less the same way we are using it ... and it excludes people who are using it differently. We have a HARD time seeing things from the perspective people in the other tribes.