Why did the gold standard fail?

If the classical gold standard worked so well, why did it break down? It broke down because governments were entrusted with the task of keeping their monetary promises, of seeing to it that pounds, dollars, francs, etc., were always redeemable in gold as they and their controlled banking system had pledged. It was not gold that failed; it was the folly of trusting government to keep its promises.

- Murray Rothbard