The problem of a trust backed system is that you can never trust the govt to let the economy work because you can't trust the govt to take an L and live in austerity unless made to.
Like with Recessions. Recessions are painful, yes, but necessary to reset economies that are too far gone in inflation. Inflation caused by the govt own spending. Trying to beat a Recession back by stimulating the economy defeats the purpose of a Recession: Saving Money and Lowering Prices.
Now, physical currency can force a govt to behave because austerity is innately a part of it. Run out of gold, then go home. Spend all your silver, cry me a river. Once the money is gone, you are forced to address the problem quicker because you are faced with the consequnces faster.
Ideally, you tie your money to some physical asset. However, even that only last until you decide to abandon the system.