[roenxi]

Loans have a cost. If the banks can borrow at negative interest rates they are strictly better borrowing the money and not lending it out compared to a 0% loan. Any profitable plan with a 0% loan in it would in theory be more profitable without the loan.

In econ-101 it doesn't matter what the spread is, it isn't in itself rational to lend at 0%. That is taking on risk with no gain.

There must be some strange contortions in place to make this work. Whatever a "loan" is these days is going to be a totally regulatory construct with little connection to what they used to be way back when.

[literallycancer]

Pretty sure you don't get to borrow from the central bank unless your product portfolio includes the retail products the central bank or government feels should be available to consumers. So you can't just borrow without serving retail.