The same reason it doesn't build it's own "plane" or "ship" or "submarine" or "satellite" or "gun" or "bullet". The DoD's job is defense, so it's about fightin

The same reason it doesn't build it's own "plane" or "ship" or "submarine" or "satellite" or "gun" or "bullet". The DoD's job is defense, so it's about fighting wars, not about building infrastructure and supplies. The security of the military apparatus will stay in the DoD. The implementation and operation of the security infrastructure will be delivered by government contract.