I was around when store clerks and similar servant positions started saying "Have a nice day! :)" rather than just "thank you (for the business)".
my dad told me that was to get you normalized to being TOLD WTF TO DO by these lowest level system functionaries. he been in contact with guys who'd been to USSR on legit biz (there actually was some during Cold War, mostly pro forma) and seemed to know about such things.
I've never once felt like telling someone "Have a nice day", but people now say that even outside being store clerks, etc.
Now that I think about, everyone that says that is trying some low level flex or domination work on you. Maybe it was just a corp program to try to let all the Freaks and Fairies, not to mention Niggers, created in the 1960s and blossoming in the 1970s, know WTF was in charge in the store.