i'm constantly surprised by people. you do something nice for someone and don't get a "thank you". are these people raised by morons? i mean their parents need to take some responsibility, but the bigger issue is entitlement.
no one is above saying thank you. and there's no one who will convince me otherwise. its been said that the two most important words in business (and life for that manner) are "thank you". think of all the good it can do and damage done when not used.
so pull your collective heads out of your asses (and you know who you are) and be human.