Mostly a matter of education. The working career is intended to be just 20 years long because you don’t want a military full of graybeards like myself.
Look to civilian medicine. There are certainly plenty of 30 yo nurses with 4 or 6 years of education and 6 or 4 years of practical experience who have the moxie to become MDs. But not the desire to interrupt their life and their income for the 10 or 12 years of being a full-time student / trainee they’d need to become a fully practicing post-residency MD.
A secondary matter is the fundamental difference between managing and doing. There are people who want to do and have no interest or aptitude in managing. There are also people who want to manage and have no interest or aptitude in doing. Putting either kind of person in the other role is a recipe for disaster.
Returning briefly to the MD/nurse example … There are many nurses who chafe at the over-supervision and under-autonomy of their skilled position, yet are profoundly uninterested in becoming MDs even if the process were easier. Because the nature of the work is very different.
See also further below my answers to these next quoted posts.
As said by @DrDeth, warrants are intended to be the high-skill technician roles that aren’t in the management pyramid.
As I said at the beginning of my post, the terms manager, superintendent, foreman, and worker, are generic terms from the industrial side of commerce. In more office-y environments you’ll have "team lead"s, not foremen. But they do the same work.
I don’t know that the term “Chief of staff” is all that well-defined. But to the degree it represents an assistant to the manager in formal charge of a hunk of the pyramid whose tasks are mostly about interfacing to the actual doers, not the supporters, it certainly fits.
Returning to the big picture:
The military has a couple of problems the civilians lack.
A big one is that they cannot hire into the middle of their pyramid. They hire only entry-level people and everybody moves up from that entry level. By having officers, WOs, and enlisted (which includes NCOs), they essentially break the big monolithic pyramid into 3 smaller stacked pyramids. That provides a way to hire new young people as junior officers but into the upper-middle of the complete pyramid.
The other big one is that rank = paycheck and paycheck = rank. By and large you can look at someone’s collar or sleeve and know their monthly pay to within a few dollars. Imagine if that was true where you work. Would that it were so!
The problem is that different skills command vastly different wages on the outside. Which means there is a problem paying enough for high-demand skills. There are things like extra pay for doctors, lawyers, pilots, and now some IT types. But the overarching system is tied to rank = paycheck = rank.
WOs can be thought of as a way to solve some of that, by carving out a layer for well-paid journeymen. But it’s still stuck at a wage level that corresponds to well-paid journeymen in industry, not in fancy office work like IT or research.
This thread from 2016 has lots of useful information on point:
My substantive post is #28 in that thread. Be sure to read @spifflog’s contributions as well. He was then a senior Pentagon officer involved in deciding exactly these sorts of policy issues.
Here’s another post of mine from the middle of another 2016 thread on a related topic.
And another from 2014:
And directly about education versus the layers from 2015: