As other people said, usually a lot of assets are illiquid in 24 hours. You can say I have money to buy this house, but if I ask you for the money the next 24 hours, most people will say they need more time to liquidate.

It is actually irresponsible to the users (risk management wise) to be keeping all that cash in hand 24/7. The easiest bad case example: are you keeping all your savings under your mattress?

Edit/to commenters below: I understand there are emotions, but that's simply how things work. As other fellow commenters noted, banks do not keep or even promise they do keep your money($) under their "mattress."

Say you deposited in EUR. The exchange and everyone borrows in USD, so your EUR become USD -- no way out of it. EUR goes down, and then there is a bank run. Even if as the bank were irresponsible and kept 100% liquid, they can not serve everyone 1:1 in 24h. Nobody can give you that guarantee, besides your local grocery store. We are thinking these things at the wrong scale.

We are not trying to shift blame away from FTX -- already the whole relationship was sketchy. But claims about keeping 100% USD with a 24h cashout in a worldwide scale is not something on the table right now. I get worried when people feel comfortable believing those statements.