I wonder what goes in the brains of people who can't say "thank you" or "sorry" when appropriate. Especially "thank you". Are they really like that? How hard is it to say to someone that you're grateful to them when they do something, anything for you? May be these people think they're overdoing it? And that might reduce the value of it? But does it really reduce the value of it? It's difficult to understand.
As for the "sorry"s, I am reminded of the dialog from Munnabhai where Gandhiji says to Bhai how slapping someone is so easy, but to apologize for something we've done needs good amount of courage.
I'm reminded of a proverb in Sanskrit: वचनेषु किम् दरिद्रता
It means: why the poverty in speech? Why not be generous when saying (good/nice) things? Indeed, it's not worth being so (poor).