Countries have wildly different needs regarding monetary policy. Those interests are sometimes in conflict. When push comes to shove, unsurprisingly the powerful dictate the rules: see the 2010s Eurozone crises.
They all want a stable currency, though, and the Euro is certainly that. To the point that even non-EU states have started to adopt it over their own.
They all want a stable currency, though, and the Euro is certainly that. To the point that even non-EU states have started to adopt it over their own.