it's all about their up=bringing, my kids/grandkids always were taught to say thank you from the beginning of being able to talk, express themselves- I know adults and kids who have not been taught to say thanks for anything-and they don't. I blame their parents, and ignore it- everyone is taught differently- makes no sense to let yourself be *slighted, upset, hurt* because someone else was not 'raised' the way you were. if you feel you need to say something about it- say it to the people who raised them to be the way they are- but don't take it personal- or expect anything to change.