I didn't grow up with sir and ma'am and my mother-in-law, who is 80, says she still remembers the first time she was called ma'am in a store. It made her feel old. So it is not just now, new manners, it is regional and cultural differences within the country. My kids sir and ma'am some of their teachers, because they expect it. I don't feel it is necessary. My friend from Scotland finds all the sir-ing and ma'am-ing here in the South very strange. Those are very specific titles of respect where she is from, and aren't really thrown around willy-nilly.
So, I don't think that sir and ma'am are needed to show respect, and in certain areas I've only heard them to show the opposite. In the US the are mainly used in the South and by former or current military people. Other parts of the English speaking world they are not common.
I just wanted to add that if I prefer to be addressed by my first name, how is that disrespectful? It is disrespectful of MY wishes to do otherwise. With an in-law, would it be respectful to address my husband's aunt as Aunt Marian, Mrs. Matson or Marian? In my mother's day, it would have been Mrs. Matson. I address her by her first name, anything else would seem very strange to me.