What would R6 get upgraded to? R5? Both were released at the same time - July 2020, so the upgrade wouldn't be due to one being outdated, but rather changing needs or ambitions of the owner.
My previous camera was Canon G7x Mk.2 mirrorless "point and shoot" which I used for about 5 years. It got replaced because I wanted a more powerful camera in general. The G7x is still fine for what it is, and is also 20 megapixels. You just can't change lenses on it, so it's limited in a lot of ways that R6 isn't. Perhaps I'll still find uses for it - when bringing the bulky R6 is impossible, and higher quality than a cellphone is needed (although phones are getting better and better). I still debate myself whether I should've splurged on the R5 in the first place to get the extra resolution, but at the same time I don't need poster-size prints, and storing/editing tens of thousands of 30 megabyte files can get expensive and frustrating in itself - so maybe I don't need R5; at least until storage gets larger/cheaper, and monitors gain higher resolution to take advantage of those larger images. Of course there's also the cropping aspect - I guess time will tell. Perhaps the 100mp version would be a fun upgrade if the cost isn't prohibitively expensive. But my point here is, there's not much of an upgrade from R6 to R5 unless you need that resolution, and it's not worth the extra 2.5k to everyone.
A few people I know who are into photography don't really upgrade all that often either, and a friend of mine was just telling me recently how he found a use for a very old but reliable DSLR that he had kept even after purchasing a newer camera. Actually don't know anyone who buys multi-thousand dollar cameras every few years, unless one happens to break. My father wanted a zoom camera and has been using the same one for years. The resolution is high enough for him and it works. So I guess unless the needs or wants change, there's really no reason to upgrade?
Perhaps the people you're refering to are the exceptions?
