If you give your money to the bank - sure, you don't really know what they do specifically with the fiat you brought. However, you can always pay with your debit card or withdraw your money in the matter of days. So it's not like it is completely gone. However, the risks are pretty high, because if a lot of people decide to withdraw money at once, it will probably turn out that the bank does not have enough of it, claim that it's bankrupt and people will lose. Cryptocurrencies are indeed in the wallet and nobody can do anything about it. It's more like when you have cash at home. And yet I don't think that's the main reason people like cryptos. People choose them because one can send money without needing to tell anyone the purpose and it will be cheap and fast. Apart from that, the majority sees a great investment opportunity here.