If Greece leaves the euro, the euro stops being "permanent". If the euro stops being permanent, then German euros are not the same as Dutch euros, Spanish euros, Italian euros, etc etc. It'd essentially become a currency pegging mechanism.
And, well, history just shows what's happened to every one of those.
Greece itself doesn't matter, at all, to the world at large. But the precedent Greece sets, that really does matter.
As for bailing them out: No, I am firmly against a third bailout. I want them to just outright default on all the debts owed to public sectors (IE. the ECB, IMF, and rest of the Troika), though not the 10% or so of their debt that is owed to the private sector (otherwise you get the vulture funds that Argentina has been struggling with lately). That way, you get a couple of years of pain, but then big growth, much like Argentina after the early 2000s crisis.
As for Greece being the epitome of socialism: lol. Scandinavia is your better example there, particularly Norway. Which also happens to be doing brilliantly. Greece has been a corrupt hellhole for nearly a century.
PS. The Greek retirement age is 66 and is being raised to 67 this year. Which is about the same as the UK.