I don't remember the exact book I read it in, but I definitely read it somewhere:
Everyone wants to have a balanced budget (here meaning reduce interest payments on already-issued debt). The problem is getting there is not easy. If you cut spending, then you will usually lose jobs, and there is no real way to avoid it. If you lose jobs, then of course some people are going to be unhappy, departments are going to be less productive, and the economy suffers.
Crucially, the people who are unhappy at losing their jobs/funding can vote you out. Also crucially, if you deficit spend, you create jobs and happy people who will vote you in.
The result is that politicians who are serious about balancing the budget (either by spending less or taxing more) are routinely defeated in elections.