Greece provides its citizens with loads of social services. Someone/something has to pay for that. In the other EU countries, you know - the ones without sovereign debt crises (Germany for example), the taxes paid by citizens help pay for some of those services.
In Greece that doesn't happen because of the rampant tax evasion. So instead the government lies about its budget deficit, borrows tons of debt, and is now hoping for a bailout from some of the more fiscally responsible EU nations. German tax paying citizens are likely going to have to help subsidize Greek citizens who are unwilling to pay taxes.