Why do some young adults lack ambition? Is it inherent or the way they are raised?

I was discussing the topic of young adults who live off their parents with no clear display of initiative with another jelly.

We touched upon parenting styles, and perhaps these folks had been given too much during their childhood. That seemed to fail us though when examining the Kennedy family and other examples of privileged family units producing high achievers.

So do you think privilege during childhood does anything to impact the ambition of a person during adulthood? Looking for your thoughts.