During the next 24 hours pay attention to how many times people could/should say “thank you” but choose not to. How many times someone holds a door open, makes a nice comment etc and there is no response or an inappropriate response instead of “thank you”.
Also, pay attention to how many times the words “thank you” are then ignored or responded to in a different manner. Say thank you to a cashier and see if they say “you are welcome” or do they grunt, ignore or say “no problem”.
People would be SHOCKED if they realized how many opportunities they are missing due to the lack of common courtesy.
Take the time and I believe you will be surprised
Have a great day!