I was raised to refer to adults that were not family as Ma’am or Sir as respect. If they were adults we knew then Mr. or Mrs. so and so was also acceptable.
At SCHOOL...in an English class we were taught that it was rude if you didn’t use Ma’am or Sir, because otherwise you were showing a familiarity that did not exist.
We were not expected to say Ma’am or Sir to adults we were close to IF it was acceptable to them and even then if they were correcting you about something you needed to show respect for them and use the respectful terms while getting your correction.
My husband’s grandchildren insist upon calling me by my first name. I have told them, in their mother’s presence, that they may call me, Grandma, Granny, Grandmother, GG, or even Mrs. -——. Went absolutely nowhere. This, after nearly 17 years. The oldest one’s 25, so it’s not like they haven’t had time to get to know me. And, honest, I’m not the wicked step-grandmother. My own grandchildren here expected to call my husband Grandpa, and they do. And if the ones who live far away, and don’t see us very often, forget, they are instantly reminded, and correct themselves. I’m not a formal person, but unless I give permission, grandchildren should address grandparents as such, IMHO.