Some of it is also the logistics chain. A commercial enterprise can get away with purchasing a screw. A military airplane tracks the screw from its lathing, to rod forming, to steel production, to iron production + coke production, to iron ore and coke inputs. All this so that when a certain part fails all related parts can be checked for similar failures.

Apple is the only commercial enterprise I am aware of that attempts to have similar supply chain controls, and their products aren’t cheap.