This is very useful for large-format technical printouts like blueprints, for a drafting table, or for a table where various users can interact with multiple documents.
The old Microsoft Surface Coffee Table project was something like that but the whole screen was 1024x768.
It's not an "esoteric" use case. Every building in the world goes up based on large-format construction drawings. For a large building that's maybe 75 sheets printed at a cost of $3 a sheet.
So you have have a $225 set of prints for every project your company is working on and you have to roll all those prints up and store them in between uses. It doesn't take a lot of those prints before you've justified a very expensive display.
Showing these files on a digital monitor is like looking at an elephant through a magnifying glass and until now no digital standard has allowed showing these files at full size and resolution simultaneously. You must zoom to read the text.
This is just monitors catching up to the resolution that large-format printing has had since the 60s. It's also useful for restaurant menus, movie posters, mall map kiosks, transit maps, airline status displays, bulletin boards... anything you want to display to the public where they can't pan and zoom the way you would on a personal device.
There are plenty of uses for a 16k video standard. It just probably isn't going to be your home television.