^^^You're so right...a thank you DOESN'T cost a thing. I think that it benefits both parties...the person who gave and the person who received. I've also been guilty of having the best of intentions, and letting a thank you slip my mind. That warm-fuzzy feeling is totally lost when a thank you must be prompted, however. And it sours the spirit of giving when someone goes out of their way to make an announcement about their choice to withhold their giving to a select few who "pay" for something they're given with a thank you.
Gollytwo, since you DO feel it necessary to make your intentions known, I'm glad you got that off your chest. I hope it helps you feel better about situations where you felt your kindness was taken advantage of.