washingtonpost.com: Opinions on Attire Not Quite Uniform: "The unit normally runs the military's National Training Center at Fort Irwin, Calif., where it scrutinizes other units in microscopic detail and brooks no deviation from military discipline."
Anyone who knows anything about Ft Irwin knows that (1) that's not a true statement, and (2) the OPFOR vehciles looked like rolling gypsy wagons every time they hit the road. There was never a shortage of coolers, sleeping bags, and hibatchi grills strapped on the backs of the Sheridans they used. Everyone was always in an impeccable uniform, even in the field, but they were rather pragmatic about their vehicles.
The NTC is run by a headquarters that supervises the Operations Group (who really runs NTC) the NTC Support Battalion, a maintenance unit that does not head for the field very often, and the 11th ACR, whose job is to play the bad guys when units come to train. The certainly do not "run" the NTC. And the "military discipline" that is referred to is most often enforced by the combat-veteran NCOs of Ops Group, who offer their sage wisdom and life's lessons to units they evaluate as O/Cs (observer-controllers) during the exercises.
Don't forget that everything the Army does is for a reason, and you might not understand it, but that doesn't mean that someone doesn't think it's the right thing to do. It's rare that people invent stuff to do just for the sake of doing it.