Because they don't have destitution motivating them to grab on by the skin of your teeth to any income whatsoever.
But, I want to note, that's a good thing. One of my college classmates is a severely messed-up person from being raised by abusively money-hungry and careerist upwardly-mobile parents from India. Having the fire of destitution in your belly is how you breed Goldman Sachs investment bankers, not good citizens of a developed society.
I agree that it can be a really bad thing. Just as your upbringing can influence you to become curious, willing to learn and self-motivated, it can also teach you the wrong kind of motivation. I have seen people come from a background where wealth was considered more important than anything, where opportunism and exploitation are acceptable means to a materialist goal, and saw these people turn out as criminals and con men.
But, I want to note, that's a good thing. One of my college classmates is a severely messed-up person from being raised by abusively money-hungry and careerist upwardly-mobile parents from India. Having the fire of destitution in your belly is how you breed Goldman Sachs investment bankers, not good citizens of a developed society.