We're all officers first and Pilot/Nav second.
How would you run a career pattern if you only had officers for exec positions?
Where would your junior pilots come from?
I wouldn't have joined to be a pilot as a Sgt - it's a career choice as well as a profession.
Then you get the problems of SNCO pilots trying to hold their own in a HQ/TGHQ/DOB/FOB with a whole host of junior/senior officers making the decisions.
Don't get me wrong - almost all NCA could easily be Pilots/Navs as they have the aptitude, but for instance would they have the presence to be a multi-engine aircraft captain? Dealing with 14 crew and over 200 passengers, stuck halfway round the world can be quite challenging
Especially if they all seriously out-rank you.
This subject has been around for years - the best NCA are going to get in the current climate is the chance to be an S02 in a specific post to cover the shortfall of Sqn Ldrs