Wouldn't the difference in the way they are used account for some of that? People shooting the 7D II would tend to use multiple shots per shutter button push than would those using the 80D, right? That would be on top of shooting in situations where you take many more pictures, as in sports.
I don't know very many, if any, 7D Mark II shooters who use a 7D Mark II alone for anything much other than sports/action/wildlife unless they're using it in a multi-body situation where a FF camera (or two) will have a lens (or lenses) covering wider angles of view and a longer lens on the crop body. Those other types of shooters you describe tend to use 70D/80D types of bodies if an APS-C body is their primary camera. If their budget is extremely limited then they're shooting Rebels of one stripe or another.
I do know one guy who puts a 70-200 on a FF 1D X (because that is the lens he uses for most of his published frames), but also carries a 7D2 + EF-S 17-55mm f/2.8 IS as his "wide" body for photojournalism. But then again, he is a "weekend" part-time freelancer so most of his assignments are very sports/action oriented - local "fun runs" or more serious running events, bicycle races, dragon boat races, people dancing at outdoor concerts and other weekend events, etc. in addition to high school and youth league sports.
Insofar as it applies to the rumored upcoming "90D" being a suitable replacement for both the 80D and 7D Mark II, those types of shooters requiring high frame rate, high volume shooting in an APS-C body aren't going to disappear into thin air just because Canon no longer offers an APS-C body with tank-like construction and a more durable shutter than what the x0D series has offered in the past (up to and including the 80D).
Many of them might well disappear from the
Canon ranks if Nikon offers an updated and improved D500 successor in the near future, though. The biggest impediment there is the high cost of Nikon's incredible AF-S Nikkor 70-200mm f/2.8E FL ED VR at near $3K. APS-C sports/action shooters are using APS-C instead of FF bodies to reduce the cost of lenses with the speed and reach they need as well as to get higher frame rates without spending what a 1D X/1D X Mark II or D4/5 body costs. The cost difference between the EF 70-200mm f/2.8 L IS III and the AF-S Nikkor 70-200mm f/2.8E FL ED VR is probably enough to buy an extra "90D" for when the first one wears out or can't handle the punishment shooting in harsh environmental conditions.