To be honest, if banks were the custodian of my cryptocurrencies, I wouldn't mind because the chances of my crypto being lost is going to go down drastically and if it was in an unlikely event got lost, the banks will have sort of insurance that will be in place to take care of the losses.
You are missing the whole point of bitcoin, you are supposed to be your own bank, I know this is not easy but the current system relies on too much trust in third parties that are known to abuse that trust.
Satoshi realized this and created a system that did not relied on trust and that put the people back in control, banks obviously do not like this and they have been attacking bitcoin only to find out that there is in fact a market for bitcoin as people are tired of being deceived by banks and lose their money to them.