One irrefutable fact about financial crises is: serious reforms are never made as long as money flows and liquidity is around. Only when the flow of money stops do the responsible executives/politicians begin to act. Why? Because then they have no choice but to act.
A point which has not nearly received the amount of attention which it would deserve is that, so far, the money flow into Greece has not at all stopped since the beginning of the crisis. On the contrary, from 2010-11, roughly 100 BEUR net flowed into the country from abroad. What use was it put to? About 65 BEUR was used to pay off Greek depositors who withdrew cash from their banks and the rest to finance the current account deficit.
The more Greece (or rather: certain Greek politicians) threaten to repudiate agreements entered into by the previous government, the more the country becomes dependent on foreign lenders. As long as things go reasonably well and consensually, foreign lenders will never cut off the country’s funding. If things were to become antagonistic, foreign lenders would have all the reasons in the world to cut off their funding.
Obviously, no one would cut off Greece’s foreign funding entirely. That would cause total disaster in a member country of the EU. However, one can make the new disbursements very selective and only for very specific purposes. For example: for the import of essential goods (but not for consumption goods); for other payments which are deemed important for the economy; for those government expenditures which are deemed appropriate.
Put differently, Greece would get a “foreign commissioner” through the backdoor if it were to become antagonistic. That’s why only keeping Greece in the Eurozone can lead to the kind of reforms which are necessary.