"Quite often, Russians smile not “at”, but "about" something."

I guess in Russia one must always be aware of hierarchy; one is supposed to be subordinate to the current hierarchy; Smiling is often interpreted as mocking by the higher ups, and as a sign of condescension by peers.

Also Moscow is quite a stressful place; Men have a high chance of dying in their fifties due to heart problems, much higher chance than in other countries.