Yeah. Sir/ma'am is weird. It's basically the only formal pronoun we have and the only place you are universally expected to used them are in the presence of authoritarians like the military and the police.

Otherwise it can be used to show extra respect or to sarcastically mock somebody for acting authoritarian.

I would say the general guidelines would be always use it with police/authority figures. And it can be nice to add to a "thank you, sir/ma'am" (typically not toward children). And basically avoid it everywhere else until you feel more comfortable worth the language.