Somewhere between a third and a half of films are listed as "real 4K".
So there is actually tons of real 4K content. (And the list is just films -- there are plenty of streaming TV shows in real 4K too, like Mrs Maisel.)
There might be another reason for the misperception -- it's true that film editing is generally done in something lower-quality like compressed 1080p, but that's just for speed/space while you work. All the clips "point" to the 4K originals, so when the final master is produced, it's still produced out of that "real" 4K.
The top link in the reddit thread disproves what you're saying though:
https://4kmedia.org/real-or-fake-4k/
Somewhere between a third and a half of films are listed as "real 4K".
So there is actually tons of real 4K content. (And the list is just films -- there are plenty of streaming TV shows in real 4K too, like Mrs Maisel.)
There might be another reason for the misperception -- it's true that film editing is generally done in something lower-quality like compressed 1080p, but that's just for speed/space while you work. All the clips "point" to the 4K originals, so when the final master is produced, it's still produced out of that "real" 4K.