Hm... regional similarities in some ways, not in others. I still find myself saying "yes, ma'am" or "yes, sir" unconsciously to waitresses and airline agents. But endearments in speech... less so. I was a social outcast during my teen years, and really did not begin to socialize until MIT, which has probably warped my language usages (and other things ;).

I rarely use "sweetie" as a passing endearment, as for me, it's a bit like using "friend" or "spouse" similarly. Sometimes I'll use it to open an email to, well, a sweetie.

"Dear" is added on when I'm feeling affectionate towards someone in that moment, but usually only for partners/sweeties. Occasional but rare use with closer friends, but I have to be careful that they then don't parse it as a diminutive.

"dear one" has always been reserved for patgreene, as has "dearest," except in occasional email salutations to partners.