Because no matter what happens, no matter the results, they can blame some one/thing else for their lack of progress, and claim they need more money to throw at it.
Weapons systems, force structures, training, all are supposed to produce a result that can be evaluated for efficacy and function. Gee whiz, that's hard, and evaluation of those in times of crisis is unforgiving. No grading on a curve, no do-overs, it works or it doesn't and people can be held accountable for the results and the spending that produced them.