I agree 4k at higher fps is way better most often he time. Just one use case people may not be aware of for 8k is video editing. You need really high resolution for editing videos else you're at risk that you introduce artifacts and blurriness when editing. Especially if you decide to zoom or crop.
This applies even if your final video is 4k.
Again, I'm on the 4k120 boat. Just wanted to share one common reason 8k is desired by some people.