As Nava implies, it has to be taught from the home. My parents, while they had their faults, always used the respectul version of “you” in Hindi because they knew I would learn it too, and they always insisted I say “hanji” and “nahji” and “yes” instead of “yeah”. To this day when my SO says “Yeah” I still don’t like it. I know he is not disrespecting me, it just sounds kinda crass.
I haven’t noticed that about New Yorkers. Granted, I am one, (though an upstater) but I find that they do say thank you. It is short, as everything has to be, but New Yorkers are no less polite than anyone; they just expect everything to be done on a time frame.