@Gyryth There is no way to tell exactly what is motivating any particular player. However, as a general matter, I think I am correct. If you want to style your reticence to rematch as a matter of not feeding into the ego of a defeated opponent, that indicates to me that you view the game of chess, at least in part, as a means of obtaining a psychological/emotional reward. That's falls in line with my general theory. People generally do not like to rematch because they do not want to risk losing after winning (or, losing again).
"I'm not going to dignify these ego-seeking losers with another game" is another way of saying "I'm not going to risk my psychological well-being because I know there's a chance I will lose."
This is not necessarily a bad thing; it is human nature. Were it not for the clash of egos, and the desire to come out on top, chess would not be a game worth playing. My point is I find the alternative explanations tedious and, based on my personal experiences, not credible - especially when the overwhelming majority of players *immediately* move to another game, with another opponent, after either winning or losing (more often after winning). Where in that infinitesimal interval of time they can manage to cook dinner, use the bathroom, babysit their little sister, or analyze the game "in depth," is beyond me.
The only thing deeper than the raw psychological panic that causes people to run from a rematch is the ocean of excuses people concoct to avoid conceding the existence of their raw psychological panic.