Thank You!

Thank you. 2 simple words designed to convey appreciation and flattery for a job well done.
My 2 year old is ridiculously polite. He says please and thank you for everything,  every time. We are clueless as to where these manners came from, my guess is Dora or Mickey Mouse Clubhouse. My 4 year old not so much and my 13 year old, well she is 13...
Does this mean my kids love me less and appreciate me less if they don't say thank you? NO. It means they express their appreciation and gratitude in different ways. My 13 year old will help more,  or play with her brothers,  my 4 year old will draw me a picture.
Do we have to hear THANK YOU to know that someone is greatful,  no...but unless we are around them enough to see or feel gratitude in a different way, then our options maybe limited to verbal communication.
During this especially busy time of the year, I want to try to communicate my gratitude as often as possible.  It will be interesting to see how it works in each situation,  but I am convinced that conveying gratitude and appreciation in am audible and visible way will make others feel as warm and fuzzy as it makes me feel.
Maybe I should thank the delivery man who just woke up my napping child first...
It is 12:30 in the afternoon.