Actually, Lala, they don't. They borrow money (capital) and pay back only interest, some loans are not repaid for hundreds of years (the slave one came out recently) by which time the value is much smaller.
Secondy, if the economy was growing a la Keynsian Economics, the percentage value of all these loans reduces. There was always an alternative to austerity 10 years ago, as above, it was a political decision to reduce public services and screw the public sector employees ( your good self included).
The irony for me about all these economic arguments recently is that Gordon Brown's Government decided to reduce the chance of a recession in 2009 by continuing to invest in big projects, to produce a soft landing, and was derided by the Right for so doing, Our man Rishi, with similar desperate economic and unemployment outcomes, is doing the same, and being lauded by those same figures.