Except if you are one of the influential countries.
We have learnt that by seeing Greece's problems.
The Euro does not permit sufficient flexibility for economies out of sync with Germany.
Austerity solutions visited upon them by creditors have resulted in worsening outcomes and ultimately have ruined the country.
They need to have their own currency back. It's the only path they have.
But it also sets the precedent for other economies suffering due to the Euro obsession. If you are in trouble, jump early.