You can do that as well in many EU countries. Without being rich.
But, interestingly, few people do. And those who do seem to take on less risk than their counterparts in the US.
Where I was born, everyone has money and people are generally modest: do not need ferraris or whatever so they just want a happy relaxed life. And that is very easy to get here. I worked very hard since I was 15 as I wanted (and have) (not ferraris but travel) more, but I was never interested in money or fame that can get someone kidnapped. I believe if I lived in the US, my parents would have sent me to Stanford or something and things might have been different somehow. I will never know: I like not having stress, at all so no regrets.
To be clear, I don’t grieve the lack of Ferraris. But the lack of ambition and related consequences gets to me.
A safety net may lead some people to experiment and play with things, others to slouching off. This even applies outside the public sphere. A stereotype of a bored millionaire's son with no energy to do anything substantial exists for a reason.
I would prefer just taking every 21 year old and saying "here is 15 grand, go do something amazing".
I don't know what the results will be, but a fair number will be worth the risk.
On the other hand, I actually like this idea. It would help people escape abusive situations, and I generally think it's fairly ridiculous how we ask young people to live on so little money while educating themselves. I just don't think it would cause many people to "go do something amazing".
But like you I like the idea ...
Me? I didn't have a chance to "try" things. My room for error was zero. Must get above 90 average. Must get scholarship. MUST find job. MUST be there at 9AM. MUST pay rent.
Now I am saving money to take one year off to work on my own thing, but only because my first future ex-wife works for NYC and I can be on her insurance. Without that safety net, at 40, no way.
So, not everyone can be born a failson like Jared Kushner, but what we CAN have is a safety net to let people take risks.