The banks will demand payment.

Take a look at the struggles of Greece. It came to a head when debt repayments were due and they almost defaulted. The interest on the debt might be manageable while interest rates are low....but when interest rates go up we might find much of our tax dollars that should be spent on services and infrastructure is instead being spent to service the existing debt - providing NO VALUE to tax payers. These debts are intertwined with our super funds and bank accounts who are invested in government bonds (debt) so if there is a default on it then peoples life savings can and will be lost.