As a modelr of all thing military, rather than just one genre or the other, I see this as well: Part of the issue with Armor vs Aircraft is that, unlike aircraft kits, armor kits by their very nature tend to build up very quickly, in a just a few hours, whereas aircraft can take quite a bit longer due to the amount of interior detail work being substantially higher than armor on average...
With the open cockpits, pulled-back canopies, and/or plexiglass noses/turrets, vs a couple open hatches with no interior lighting, aircraft are more complicated... The amount of post-assembly detailing in the Armor world is generally in the external stowage/painting aspect...
Aircraft, generally speaking, also have much more complicated paint-schemes. In an average, four-hour work session, I can knock a tank out to about 80% complete... After four hours with an aircraft, I'm at about 80% with just the cockpit or engine...
I also tend to get much more involved in researchng and detailing aircraft models than I do armor kits, simply because aircraft interiors are more interesting to me, vs tanks and AFVs, as they're "too much like work" in that I lived in them in the real world, vs only "being around" some aircraft, and up close and personal to even fewer, and actually flown in fewer still...
Also, being a diorama builder, if I'm working on an armor diorama say, once I complete the tank to the point where it's time to go on the diorama for attachment and final assembly, the WIP goes there as well, and probably seems unfinished to the Armor Forum members... Same-same for aircraft...
That's when the other sub-assemblies of diorama construction start,e.i: base, terrain, structures, figure-selction and modifications, etc...