Common 'Duh'

I say common "duh" instead of common sense because isn't it a "duh"?

I mean what the heck is wrong with people?? When you hold open a door for someone...I would like to hear a thank you....not because of my act of kindness, but because someone did something for you and you should validate that! I love it when they walk past me not saying a word and I yell out OH YOUR WELCOME...and they just keep walking!
Or if someone sneezes, my natural response is to say...bless you. Is that odd? Are you not supposed to do that? I mean am I offending people now?
Crazy words and/or phrases I grew up with are: thank you, I appreciate that, you're welcome, hello, have a nice day, how are you, etc....
Is this lingo old school? Am I out of touch? Are you no longer supposed to look people in the eye when you speak to them? Or ignore them completely? Perhaps this has all been an misunderstanding on my part...I assumed we were all on this planet together, living, breathing the same air, sharing similar tragedies and happiness...so I guess I ASSUMED that we all should be there for one another, even if it is just a small thing like "thank you."
But is "thank you" really such a small thing? I mean take any moment in your life, whether it is something small like holding a door open for someone or being there for a family member/friend...and they say thank you. Doesn't it feel good to be appreciated? Good to be acknowledged and validated? You don't need a billboard announcement, but those two small words, even from a stranger, can change a mood.
So when you are out holiday shopping this season with all the crowds, let us not forgot common sense and courtesy. Even if others do.