Consider this:

To use a 32" 4k monitor, you need to place it at the same distance as a notebook, so you can see it just like you see a 16" 1080p screen (you wouldn't push that screen farther away).

Now if you replace that screen with a 65" 8k, you'd need to keep that distance, and you'd end up with a ginourmous screen very close to your face. I just went close to my 65" TV and it doesn't make sense.

Either you place the screen close and your eyes get tired from movement, or you place a larger screen farther away and get tired from focusing on distance.