First, structure the organization to maximize productivity. Efficiency will follow. Spans and levels would self correct. It is the RESULT of proper organization, not the primary objective.
But instead, when the crisis hits there is no time to look at things carefully so, we can easily cut spending by peanut buttering cuts or just forcing a spans/levels metric.
Also, a dirty little secret from observing large, old, very bureaucratic organizations like Intel... The people on top didn't build the org and if they are honest they will tell you they don't really understand how it actually works together. It has taken on a life of it's own. They are not even competent within the organization to really restructure... so the next best thing is to pick some metric and just make that the forcing function.