On the planet? Many people. Maybe you're thinking 12K or 16K.
The value just wasn't there and probably won't ever be for most use cases. XR equipment might be an exception, video editing another.
It's uncommon, sure, but as mentioned it was sold to me as being a development board for future resolutions.
Someone else probably said that years ago when everyone was rocking 1080/1440p screens.
What gamers look for is more framerate not particularly resolution. Most new gaming monitors are focusing on high refresh rates.
8K feels like a waste of compute for a very diminished return compared to 4K. I think 8K only makes sense when dealing with huge displays, I’m talking beyond 83 inches, we are still far from that.
Which would then imply that you don't need a display as big as 83" to see the benefits from 8K. Still, we're talking about very large panels here, of the kind that wouldn't even fit many computer desks, so yeah...
How many of the cards of that time would you call “4K cards”? Even the Titan X that came a couple of years later doesn’t really cut it.
There’s such a thing as being too early to the game.