As a southerner that's how I have seen it for years. I'm 64 years old. I address people I don't know with "sir" or "ma'am" regardless of age (not that it offends me if someone doesn't do that--and if someone says, "Please don't" I certainly respect their wishes).

I've referred to many a teenage waitstaff with "ma'am" and "sir" when I don't know their names.

Funny though, I don't like being referred to as "Mr. Willis"! 😎 Culture and cultural mores are constantly changing--so even these terms fall into disuse.