Minting a currency is a crime punishable by death in almost all of the kingdoms of the Hyborian age. Kings are loathe to give up the power to regulate the currency of the kingdoms.
There was one attempt, years past, to make an independent currency built around the principles of free exchange and free markets. Unfortunately, the necromancer who invented the idea was executed before it could take root and his crypt-o-currency was forgotten.
