I think people are like every other creature. We seek pleasure and avoid pain. Evolution uses this method to get us to stay alive long enough to reproduce. Simple. The only problem now is that we are capable of seeking almost unlimited pleasure at the expense of the future. Willpower and long-term planning can wait because I can resist anything but temptation.
On the other hand, as you suggest, we have a hard time changing our minds because that would require the realization that we were wrong. Oh, the humiliation, the guilt, the embarrassment! I can’t have that. I’ll just keep believing I’m right, thank you very much.