Fiat money tends to create huge bubbles, which, when they collapse and they always collapse lead to extended depressions and severe hardship, especially for ordinary working people and seniors. Effect on the banking system. In effect, banks traditional role as intermediaries between savers and borrowers decrease, and the banks become the equivalent of hedge funds whose downside is guaranteed and subsidized by ordinary working people. The euphemisms for these guarantees are called the lender of last resort bailout facility at the Federal Reserve, and so-called Federal Deposit Insurance, which is not insurance. Likelihood, duration, and size of wars.
Wars cost money.
Since the only sources of revenues with commodity money are taxes which people tend to resist or borrowing which drives up interest rates there tend to be fewer and smaller wars. For example, it is less likely that the U.S. would have fought in Vietnam if President Johnson had to finance the war with taxes. Fiat currency enables politicians to generate revenues with less accountability. They are then able to act without the consent of the citizenry, which, if consulted, would probably allocate their savings differently. Thus, politicians have a freer hand to engage in military adventurism, and they do.