People here seem to be really competitive when they ride to work. I see teenagers riding to school who are in groups and chatting, but it seems we adults are all trying to win some kind of race. Yeah, sometimes I'm one of them.
Perhaps it comes of living in a car culture. We've lost the habit of engaging other commuters because it's impossible in a car.
I don't particularly want to chat while I'm commuting, but I do think that if I say "Good morning" to another bike commuter I should get at least a nod back instead of a surly blank stare. What's up with that?