A fiscal union led by Germany would in effect force debtor nations who want more German and ECB support to surrender more of their fiscal sovereignty, in a binding way, to EU Commissioners, who would have greater authority in shaping national budgets and fiscal policies.
Rather than ECB bond buying or a common bond issuance being a solution to the problems, those activities are only possible once the solution is in place. Needless to say monetary union was a significant surrender of monetary sovereignty. However, by retaining fiscal sovereignty, countries found an escape hatch. A move to fiscal union is to close this loophole.
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