I want 4k/5k and an 18"-21" diagonal, but all the hi-dpi smaller screens go to laptops and tablets, I guess. No monitors like that. Hell, under 27" and 4k can be tricky to find these days. 24" models exist but are a shrinking category.
I don't want or need my monitor to take up a huge amount of space. But I do want high pixel density. Looks like I'm in too small a market to serve.