The problem is that, in a world of floating exchange rates, as Italy was before the euro, if one country is subjected to a shock which requires it to cut wages, it cannot do so with a modern kind of control and regulation system. It is much easier to do it by letting the exchange rate change. Only one price has to change, instead of many.
Milton FriedmanGovernment has three primary functions. It should provide for military defense of the nation. It should enforce contracts between individuals. It should protect citizens from crimes against themselves or their property. When government-- in pursuit of good intentions tries to rearrange the economy, legislate morality, or help special interests, the cost come in inefficiency, lack of motivation, and loss of freedom. Government should be a referee, not an active player.
Milton FriedmanTo the best of my knowledge, there has never been a monetary union, putting out a fiat currency, composed of independent states.
Milton Friedman