They remind us that if you push on the system in one place - altering an assumption or an implicit equation - it will have consequences elsewhere. Those little ad hoc adjustments policymakers find so convenient are not a free good. Researchers set high standards for analytical rigor. Policy must have a sound intellectual base.
Policymakers should be able to write down their models, even if in only a sketchy literary form. If those models cannot be articulated, they are probably flawed.