What you have in your bank account is not digital cash. It's effectively a note that the bank owes you cash.
This may sound like a technical detail but as far as I understood without physical money there would be no bank accounts. That's what I always wondered about: how could an economy go 100 percent electronic banking, if banking is built on the existence of physical cash?
This is the missing link. With those accounts you actually would be able to own electronic cash.
That said I have no idea how this would work in practice. Maybe you would have the payment option to pay with this electronic cash. But why would you pick one over the other?