At least for now, it is necessary. Because while there are definitely a lot of people that are 100% bitcoin/crypto, definitely not everyone is willing to take the volatility risk. Not to mention not everyone is technologically literate to hold their funds securely.
In terms of usability and knowing the risks you've mentioned, banks aren't THAT bad for use. It's just that I don't think you should be putting literally all your wealth on a bank.
Agree, whatever it is, banks are still needed by us, considering that crypto doesn't have physical money. We have to cash out bitcoins, we have to go through our local bank and we get cash. So whatever it is, we still need a bank as an output from the results we get. Moreover, not all countries ratify payment instruments with bitcoin. So the solution is not to put everything in the bank, for me the bank is only my output to take money to buy something o