I wanted to make a comment explaining how banks are different because they lend that money back out - it's not like they don't have it, they just don't have it liquid. Regulations are very strict about what percentage they must keep available. Also there's things like FDIC insurance. But at the of the day they are something akin to a government sanctioned ponzi scheme. It's true that if everyone asks a bank for their money back at the same time, the bank will fail.

I imagine you're bringing this up to say that crypto is no worse than traditional banks. I disagree strongly with that.