I generally agree that "the grass is greener" is common for IT people I think. It's a huge field, and you hear about people doing cool things all the time.
But on the flip side, that one cool thing might be the ONLY thing they do, all day, every day, which might not be as cool after 6-10 years.
But I do think your point about benefitting large numbers of people is a strong motivator..that's partly what academia relies on to keep employees as below-market rates -- the mission oriented drive to make the future better. I don't mean to poke at that issue specifically, but it's a great example of how teachers, etc. will continue to work for pennies as long as they can afford it (it's almost abusive).. but that drive is a critical part of their personal happiness