Why governments (or the ECB) do not buy bonds directly?

The rescue package for Greece includes new financing for 5% p.a. Our politicians say, this is a good deal as the German state for example could refinance for 3% p.a.

Some of the aid for Greece is to enable Greece to repay bonds mature within the next 3 years, some is to finance the current deficit. In my opinion the EU governments are wasting money in the benefit of the  "Spekulanten". Why does the aid package not include the direct purchase of Greek bonds maturing within the next years? The yield is far above the 5% level and this could trigger a serious short squeeze. It will also show to the markets, that investors lose some yield, if they sell bonds on distressed levels.

I would bet that not much bonds will be offered by investors if they know that there are continous bids in the market.