The number of times that gold standards have been ended isn't proof that gold standards don't work. It is proof that people in power will remove obstacles in the way of achieving their agenda.
People in power are still people. People cannot be trusted to be responsible with massive amounts of money when there is no personal penalty for being fiscally irresponsible.
Now we (Americans) don't have such a silly constraint and launch all the wars we want. No need to even call them a war or to ask for permission. Or even notify the public that one is being launched. Funding is already secured.
This doesn't prove that the gold standard was bad for the people.
Governments grow until they collapse. That growth eventually is constrained by the inability to print gold.
This is particularly obvious if you consider that dropping gold and silver from currency is near the first thing to happen when war starts. Inflation is a hidden tax. Governments use it to continue their largess beyond what would be possible with direct taxation.
> I can think of a single case in history where policymakers decided to reverse
Everyone knows politicians are liars and cheats. Why would the actions of politicians or those appointed by them be a signal of virtue or correctness?
While I can understand why something like the gold standard serving as a fiscal straitjacket could find appeal, I can't understand why people ignore the repeated demonstrations of its ineffectiveness in that role.