You can lose access to regular accounts as easily as to a blockchain. In fact, losing database of your password manager is even worse, because even if you have backups, they’re not going to be complete.
With a blockchain all you have to worry is your private key. And you can write it down on a piece of paper, if you want, and put it away in a safe or a bank vault or something. Then, if you use it to restore your access years later, nothing will be lost.
“There are 2 types of people in the world: those who make backups, and those who don’t make backups yet.”
Well, why would banks replace the system which allows them to charge fees for every other interaction with their services? A blockain solution would allow multiple different banks (and, possibly, even regular people) to access the data with no middlemen, and, therefore, no fees. Or, well, no fees that directly end up in the bank’s pockets as profit, that is.
Getting rid of that is bad for business. So, unless something magical happens and the EU, for example, pass a law requiring the banks to switch to a more de-centralized, more fair system, it’s not going to happen.