It's an American thing -- I've found it's very common in the US to address random strangers as "sir", and it's used among people on the same social level. In o

It's an American thing -- I've found it's very common in the US to address random strangers as "sir", and it's used among people on the same social level. In other English-speaking countries I've been to, "sir" is a genuine sign of subservience.