The founders I've known were already wealthy when they decided to do a startup. They aren't at risk because even if the startup falls through without making a cent they have enough money in their bank account to withdraw $200k/year for thirty years. There's no risk there.
Most can even file for personal bankruptcy and then lounge around in their parent's home for a bit. (Or a house in the name of their spouse-with-a-prenup.)
My parents didn't have a garage for me to found a business in.
When people helpfully suggest, why don't you start your own business, they usually have a substantially bigger than average support network and liquidity to begin with. I never get those suggestions from people who've actually experienced hardship due to job loss or financial stress.
