Quite. It's entirely rational for the government o maximize borrowing when interest rates are low, because treasuries are fixed-income securities, whose coupon (regular payment of interest to bondholders) does not fluctuate with the interest rate. Now if rates go up and borrowing does not fall, that would be a huge problem. But when rates are historically low it's completely rational to load up with as much debt as you can carry if the economic gain > the interest payment. My main beef with governance (by both the parties rather than one alone) of the last few years is that we didn't borrow enough and what we did borrow was mostly spent on transfer payments, instead of a massive (and necessary) overhaul of our infrastructure that would have created more employment and arguably had a greater money multiplier effect even at sub-optimal levels of economic efficiency.