Adam Smith had an insight that elegantly answers the question:
The practice of funding [i.e. borrowing to pay for government spending] has gradually enfeebled every state that has adopted it...where national debts have accumulated to a certain degree there is scarce I believe a single instance of them having been fairly and completely paid.
He, of course, was writing about England. And with the UK government now repaying its creditors in devalued, inflated sterling, he seems to be right there, too.
