A better question might be, why is Space Force using a military rank structure of any sort?
Our current system dates back over 2,000 years. You've got officers making policy, non-commissioned officers implementing policy, and the grunts that do the majority of the fighting. Doesn't matter if it's Centurions, Decurions, and Legionaries, or Colonels, Sergeants, and Privates. The purpose is the same.
The military rank structure (and the rules establishing them, whether they be the Articles of War or the Uniformed Code of Military Justice) has one overwhelming purpose: The application of lethal force in the service of the country. Primarily this application is against the enemies of the country in question. But it also establishes the use of lethal force against one's own troops if they fail to follow orders. In combat, NCOs were "file closers"... men who would shove replacements into the front lines as soldiers were injured, and would prevent men from deserting their posts in combat. NCOs were expected to summarily execute men trying to desert. "Pour encourager les autres" is the pithy French term for this: "To encourage the others."
But the situation in Space Force *isn't* the same. No one fights. Just about everyone works in a quiet office or maintenance environment. And if Space Force ever has manned vehicles? The US has *never* sent a non-commissioned officer into space, nor even a lowly private or airman. Those that were military were all officers...occasionally accompanied by ordinary civilians. This is a complete inversion of the traditional purpose for military ranks.
So...why does Space Force need E-1s? E-6s? Why force technicians into enlistment contracts? Why not make them civil service, instead?
Kipling wrote, "The 'eathen in the darkness must end where he began, but the backbone of the Army is the non-commissioned man." But Space Force isn't an Army. If you've got an excellent technician who can run a maintenance team, give him appropriate Government Service rank. He or she doesn't need stripes on their sleeves, nor the mickey-mouse associated with the military command structure.
Ironically, this is something that Star Trek got: All member of Star Fleet were officers.
And, in fact, Space Force probably *does* need commissioned officers. An officer with a commission is a representative of the government, and thus if Space Force ever DOES perform any military action in space, the people in charge of it probably need commissions.
Ironically, most of the above applies to the Air Force as well. Maybe in 1947, 60% of the bomber crews were enlisted, and the Air Police protecting the bases were mostly sergeants and airmen. But even the BUFFs don't carry gunners anymore, and base security is mostly non-enlisted security cops.
Ron Wanttaja