I'm not rich, neither can I cite evidence to back this up, but looking around in my circle of friends, I don't agree with you.
Rich(er) kids have just as much drive to work on interesting products, find new solutions to problems, etc. And they have the added benefit of not having to worry about making a baseline salary on the side, they can ask their parents to bootstrap them, to find first clients, etc. Sure you can say that there are some who are slacking off on their parents money, but then again there are also middle class/poor kids who don't do anything useful in life.
Allow me to rephrase then: to the extent that lack of comfort/possessions motivates people to strive for better, rich kids will experience less motivation from that source. Of course they can always find motivation from other sources. I suppose you could also argue that everyone is motivated to maintain their current standards of living, rather than (or more than) elevate to something higher. So rich kids will find it unacceptable to settle for a middling income.
Rich(er) kids have just as much drive to work on interesting products, find new solutions to problems, etc. And they have the added benefit of not having to worry about making a baseline salary on the side, they can ask their parents to bootstrap them, to find first clients, etc. Sure you can say that there are some who are slacking off on their parents money, but then again there are also middle class/poor kids who don't do anything useful in life.