I grew up at a time when Courtesy Titles were required. All of my friends' mothers were Mrs. xxx and their fathers were Mr. xxx. There were maybe 4 or 5 adults were were allowed to call by their first names. If you didn't know whether the woman was married , you used Miz xxx. This was the 50's in the South - way before Ms.
But, as late as the 80's - mid 80's, they were a problem. I worked at IBM in New York. The New York Times had a rule that everyone had to have a courtesy title. My job required me to be interviewed by the press. When the New York Times called, because of their rule, they required me to, in effect, give them private information that in no way affected the content of the interaction. They could not use my quote unless I told them whether or not I was married. If they could not use my quote, I could not do my job. (I'm proud to report that IBM backed me up 100% - they left it up to me with no penalty. And the NYT finally adopted Ms. a year or two later.)
Since then, courtesy titles have annoyed me no end. When I am required to select one in filling out a form, I nearly always select Dr. or Mr.
But, somehow, those little kids calling out Hi Miss Susan is way more endearing than Hi Susan so now I'm having to rethink the whole thing.