Addresing elders Sir/M’am is a must with the military and favored by many in the South.
In the North if you yell across a distance at a stranger to get his or her attention you shout sir or m’am sometimes at the top of your lungs. Law enforcement officers (traffic stop) use sir and m’am to show respect and equality regardless of the age.
You don’t usually say it unless you’re in the military but in the South you’re more likely to address your elders with sir and m’am and would be subject to discipline in some public schools and most Christian schools. You would probably be subject to corporal punishment in this previously mentioned Chamberlain-Hunt military academy in MS for sure