When has thank you become a bad word??!!

Just got back from doing groceries, now I should have known better than to go get them the day before Easter but what can you do, we needed food. So as I pull in to the store parking lot, it's full!!! I gather up my courage and enter the store and lo and behold, it's insane in there. Now in past experience anytime, I have gone shopping the day before a holiday people tend to be, well to be blunt, very RUDE! I, not being any better than these people, do try to take the high road and maintain some civility. I was taught to say "Please", "Thank you", "You're Welcome", when have these terms become dirty words???!! It seems like nowadays, most people don't even bother to leave the door open when you're right behind them, they just let the door slam in your face. Nice! Anyhow, if you are out and about today, PLEASE do me a favor and remember to say your "thank you's and so on". THANK YOU!!