Great comment. I just bought a new Dell 6K display and I'm struggling to imagine a purpose for 8k, but it's incredible that we have the technology to drive that.
It's for large monitors. I run a 43" 4k tv as a monitor. I would absolutely benefit from a similar sized tv in 8k. And people who run closer to the 50" size would benefit even more.
I think you're probably right about traditionally sized monitors, though.