@LukeAlmighty First there was the gold standard
But gold is hard to transport and when you are paid in gold, you cannot really prove its purity except by melting it down and assaying the resulting cast.
So everyone put their gold in vaults and began exchanging vault receipts. No one really ever took self custody because it is hard.
Soon goldsmiths inflated the number of receipts... No one noticed much except that they became very powerful.
When they had inflated so much that they risked bankruptcy, they lobbied the government to abolish the gold standard and no one paid that much attention.