"Maybe I'm missing something, but where is the for-profit motive for banks to lend, for absolutely no return?"
You're definitely missing something, because private lenders are perfectly free to charge interest. ZIRP applies only to federal debt.
"Yet, why would I, as a banker, lend to the government at all?"
Currency issuers never need to borrow. That is an incorrect statement of why Federal debt exists. Federal debt is a savings instrument, and as Europe and other negative interest rate debt has shown, there is still a market for savings instruments even at the zero lower bound.
You're definitely missing something, because private lenders are perfectly free to charge interest. ZIRP applies only to federal debt.
"Yet, why would I, as a banker, lend to the government at all?"
Currency issuers never need to borrow. That is an incorrect statement of why Federal debt exists. Federal debt is a savings instrument, and as Europe and other negative interest rate debt has shown, there is still a market for savings instruments even at the zero lower bound.
https://www.bloomberg.com/news/articles/2019-08-15/negative-...
"Negative-Yielding Debt Hits Record $16 Trillion on Curve Fright"