My problem with this thread is the (necessarily) vague definition of 'manners' in this context. I was raised to be polite, forgiving, honest, open doors, bring gifts when visiting someone's house for the first time, arrive early and leave before my welcome is expended, and to say "Please" and "Thank you" when requesting something for myself or when receiving something from someone.
Those, to me, are necessarily good 'manners' because they relate a very specific benefit to the person on the receiving end. It is nice to be received polititely, forgiven our minor
faux pas, have doors opened for you, brought gifts when people first visit you, and to have people not arrive late and not stay past their welcome.
But saying "Sir" and "Ma'am" to me connotes no positive benefit nor any sense of 'manners.' Certainly it is a title of respect, but I personally find more respect being addressed by my first name or <prefix> last name by children, if necessary. But calling me "sir" seems impersonal and even a bit mocking.
Take that for what you will.