As the Greece example shows very clearly, this does not work in the long run. By the way, this is also the reason that the gold standard failed. The gold stand

As the Greece example shows very clearly, this does not work in the long run. By the way, this is also the reason that the gold standard failed. The gold standard was essentially a currency shared by the entire world. This had some advantages for international trade, namely no or reduced exchange rate risks. However, differences in how productivity developed in different countries ultimately led to countries being squeezed out of money to the point where politicians either had to default or rule by violence against their own citizens. A currency cannot survive for very long unless there is a significantly sized central authority that balances inequalities and acts in the interest of all citizens of the currency zone.