Why do they call friends by surnames?

Question

I noticed in the states that friends and workmates are addressed by their last names rather than their given (first) name, why is that ?

Answer 1

sometimes if someone has a catchy last name their friend usually just calls them that. and sometimes people have the same first name. It can make things less confusing.  

Answer 2

It is a very old tradition in England,especially at schools,both public and government and is thought to instill some sense of equality,or humility.There could be ten Georges but how many George Fanshaws would there be?

Answer 3

I'm in the states but that's not how I roll.