It doesn't matter how confident I am in my vision. If the potential failure scenario is life-long debt and debilitating financial pain for my family and my children for their entire upbringing, anything less than 100% certainty might as well be 0%.

For many people, the decision is "I think this is a good idea, and could do very well, and could bring a lot of good to a very large amount of people, but good things fail all the time. If for some reason, the market decides not to take interest, or some competitor that has yearly turnover in the tens of billions of dollars decides to crush me, then I will be carrying the consequences of other peoples' decisions for the rest of my life, and my savings will be gone, and I won't be able to cope with even a minor medical situation, which is why I make sure to keep 5 figures in my savings account, because even with my medical insurance that I pay $1k monthly for, I can still lose up to $8k per year out of pocket, and medical insurance frequently decides to not even cover my needs anyway. I can't afford the time and effort to even sue them for what I need."

The US is not a good place for innovation unless you're already rich or the innovation is guaranteed not to fail.