I emigrated to the USA when I was 24 and have lived here for nearly 32 years. My step-father used to hate the "fake" "have a nice day" stuff in the US, but on his second visit, he realized that he was starting to like it. He knew it was "fake", but he knew that the person saying it knew too, and he came to understand that it was just a way to provide a more pleasant atmosphere. By giving into it just a little bit, a positive feedback loop starts to run, and everybody wins.

ps. my kids think that i'm grumpy, bad tempered and pessimistic :) they're right about one of them.