Moral Superiority

It's a very British thing.

If you walk around town in the afternoon saying 'hello' to complete strangers, you are judged to be insane - however, early in the morning, before the rush hour, when the streets are quiet, us Brits quite happily walk around saying 'good morning' to all kinds of strangers.

I think the phenomenon is because of the British belief that one has moral superiority if one gets up earlier than others. The 'good morning' is code for 'aren't we better than they are'.