Ezra Klein says that if we don’t pay for wars we can’t subject them to any kind of cost-benefit analysis and thus have no idea if we’re making good decisions. Diane Lim Rogers says the point is fundamentally generalizable:
The same point could be made with any other part of the federal budget that we currently give (and for a long time have given) a “pass” to when it comes to paying for it. If it makes sense that we ought to be evaluating whether the wars that preserve freedoms and save lives are worth their cost, then certainly we should have applied that test to the higher physician payments under Medicare or the extended Bush tax cuts–things that mostly “preserve” and “save” the after-tax incomes of higher-income households–a long, long time ago.
My strong suspicion is that this is why tax cuts fail to starve the beast (PDF). When you repeal the idea of a budget constraint, then suddenly spending doesn’t need to be justified. Politically disfavored programs (food stamps, Medicaid) may still get cut but things with strong claims behind them (Tomahawk missiles, Medicare, farm subsidies) are now free to run amok.