It's quite probable that they are interested in things that don't directly relate to making money. I know many senior researchers with Phd's in the UK who get paid something like 30-40K GBP - I don't know the exact figure but that's about right. They could probably earn at least 4 times that if they worked in banking or accounting but that doesn't interest them. Often they aren't even aware it is a possibility. So it's more a question of motivation rather than intellect as with many things in life.