Growing up it was common to hear "buenos días". Buying un cachito y un café en la panadería, entering a store, or even when casually crossing glances with a stranger on the street, gently nodding as you passed each other. I later moved to New York (I was looking for something). One day I got on the elevator to go down for a walk and there were a couple of people inside. I said "good morning" when I walked in, as you do. No one responded. Different customs for different places, I thought. That...