The purpose of government securities is not to fund spending but to give the rich a safe place to park their capital with interest.

You have a source on this? I find it difficult to believe that it is ever a good idea to just take out a loan for the sake of making the interest payments. Especially using public funds, that sounds pretty close to embezzlement.

Rather, a country’s budget should always make use of debt, because its reputation has value and should be invested, not left sitting on the table.