Yeah, most people probably don't sit close enough to the TV to tell the difference between 720p and 1080p - on a 55" television, you have to be less than 11 feet away. I suppose some people have very acute vision, but for the most part it's science and any perceived difference is imagined.
From 1080 to 4K, you now have to be 7" away from a 55" tv. Ummm, no, that's not comfortable to be that close.
Anyway, "8K" sells...and it's probably easier to do that than it is to improve things like the glass, contrast and color accuracy (which would be much more noticeable).