Because the Japan is able to pay their debt and Greece not. Even if the debt of Japan is double of that. Because Japan work and Greeks don't. Greeks cheat their Government about the money and the Japan not. It is not problem of Central Bank. If Greeks will have Central Bank they will print money without ceasing. Money that don't justify their state of economy. Because they are accustomed to cheat and lie about everything and with everything. After every crisis they will print other money continuously. Going down and down. The money cannot be paid with new printed money (which is the thing that do the Central Bank) BUT WITH WORK.
Following this reasoning, ECB must get punished more than Greece people, because they never work, they just print money. Unfortunately, central banks print money, rest of the people work, that's how it works, and has been working for hundreds of years
"During the Early Modern era, European monarchs would often default on their loans or arbitrarily refuse to pay them back. This generally made financiers wary of lending to the king and the finances of countries that were often at war remained extremely volatile.
The creation of the first central bank in England - an institution designed to lend to the government - was initially an expedient by William III of England for the financing of his war against France. He engaged a syndicate of City traders and merchants to offer for sale an issue of government debt. This syndicate soon evolved into the Bank of England, eventually financing the wars of the Duke of Marlborough and later Imperial conquests."
"The founding of the Bank of England revolutionized public finance and put an end to defaults such as the Great Stop of the Exchequer of 1672, when Charles II had suspended payments on his bills. From then on, the British Government would never fail to repay its creditors. In the following centuries, other countries in Europe and later around the world adopted similar financial institutions to manage their government debt."