well, personally I'm @ 25 years flight-free now. never felt like a sacrifice at all, more like a liberation actually.
but thats an outsider-position. Not like totally rare, but not mainstream either.
so the question would theoretically be: "why are people not acting in their self-interest ?"
but whatever a scientific answer to that might be, I have made up my mind - they CAN'T. Usually most people are generally unable to anticipate or even see the consequences to their actions.