They didn't produce gold, and with an alert populace, could not, for any protracted period, attempt to loan gold which did not exist. They were warehousemen in three-piece suits, guarding other people's wealth. The advent of the Euro signifies the emergence of a single banking facility for Europe. Various banks may issue euros, but their regulation, perhaps informally, by a single unit, has obvious advantages for those who might like to extend their influence beyond national boundaries. Gone, except for the freedom to conform, for otherwise is to starve.
Power tends to become concentrated.
Until relatively recently, Italy and Germany, for instance, were a collection of more or less independent feuding states, until unified as single nations. Earlier, Ferdinand and Isabella had unified a divided Spain. Japan was brought under the control of a dozen or so families. In our own country, we have seen the sovereignty of the individual states swallowed up by the federal government, whose jurisdiction was, according to the Constitution, to have been extremely limited. Local government provides its own checks and balances.