All the very serious people at the time got mad at The Crazy Left putting forth this perfectly legal, perfectly sensible idea to combat an even more bonkers idea that was itself arguably a violation of the 14th amendment ("The validity of the public debt of the United States, authorized by law, ... shall not be questioned."). So "we" let the Republicans put the gun to the hostage (country) repeatedly.
Lee spells it out. The Treasury can do this!
“The Cancel the Coin Act removes a legal loophole that allows the Treasury Secretary to bypass the statutory borrowing limit by minting platinum coins of any denomination. In doing so, this legislation ensures the powers to coin money and regulate the value thereof remain firmly
— Rohan Grey (@rohangrey) February 5, 2021