Happened to me all the time as a kid.
I have not heard someone ask a man to smile specifically in the same way I was asked to back then. I think they were just doing it because someone spread a rumor that I was "the kid that never smiled". I smiled when I wanted to, just not for those berks.
Kids say and do things adults wouldn't. I don't think I've heard anyone tell a woman to smile to her face either - but girls? heard that a lot from boys and girls at my school.