Thanking and apologizing: Talk that isn't cheap. Researchers have introduced a framework, 'Responsibility Exchange Theory,' for understanding why thanking and apologizing, as well as bragging and blaming, matter so much, and presents novel experimental studies that reveal the psychology underlying these communications. Source 8k.
Usually by culture you are taught from young to always say thanks or sorry for specific situations. I think it can be just a form of projection in order for people to feel good about themselves and doesn't want the price of "Self-depreciation" if they have to be the receiving end of exchanging responsibilities.