I think the government bonds exists since a long time and I believe that people have more faith in Government bonds as in the past there were no more options available for the investments and people were sure that their money is safe by investing in the government bonds.
Hmm... but things have changed a lot. The government bonds are not 100% safe, as evident from the instances involving Ukraine, Greece and Argentina. Right now, there is a feeling among some governments that debt can be written off, if there are sufficient reasons to do so. An example is Ukraine, which is refusing to honor the 3 billion Euro-bonds issued to Russia.