There are two ways to enslave and conquer a nation. One is by the sword. The other is by debt.
John Adams, Founding Father and second President of the United States
On an individual level, debt represents both a risk and a cost. A risk because the debt can be called, and if unable to pay, assets can be seized. A cost because a premium must be paid on the money borrowed in the form of interest.
On a national level, the costs (interest) represent services not rendered or additional money pulled out of private hands while the risks represent danger to the economy.
H/t reader David