The debt of the Greek government is so bad that if they default, it would completely colapse, all services suddenly cutoff probably leading to dangerous anarchy ...
A short, sharp, shock is the least painful way out of Greece's mess. Anything else is just delaying the solution and storing up even bigger problems for the future.
I don't agree. Sovereign debt is like a an addictive drug. A country needs to gradually wean of its debt or else it is like a shock to its system and can actually kill it. Imagine the EU as a bunch of drunkards who need to quit drinking and get back to work, Greece being the worst of them. If you suddenly cutoff the alcohol to Mr. Greece, he will go into shock and the rest of the drunks are going to panic and everything collapses.