Treasury bonds are not irresponsible. What is irresponsible is to not hedge your interest rate risk in the form of interest rate swaps. Most other conventional banks do exactly that; they have a portfolio of held-to-maturity (HTM) securities that they hedge with interest rate swaps to avoid bearing that risk. In the financial sector, you only leave unhedged the investments you are _actually_ betting on; if you are to say that they were betting on 10y bonds (until maturity) holding the same value as the day they bought them, without any form of risk management, I would consider that irresponsible.