As the Romans and many others found being able to mint coins doesn't give you as much power as paper money since you need to find the gold and silver to make th

As the Romans and many others found being able to mint coins doesn't give you as much power as paper money since you need to find the gold and silver to make the coins (debasing the currency is a great way to destroy your economy). This really limited the practicable power of government. It took a while for the idea of paper money to catch on, but once fully accepted the modern state became possible.