For me, for example. Professionals in the CAD arena love high resolutions, but also reasonable aspect ratios, because they tend to rotate 3D models. 3:2 is even taller than 16:10 (which I have - 3840x2400 with 208 ppi), but not as tall as 4:3 aspect monitors, which have unfortunately completely vanished.
This aspect ratio allows to view two A4 pages next to each other, such as when reading some online pdf catalogues. The Digi-key one is an example, some 2000 (4000?) pages with small fonts, but easily readable on a 4k monitor, two pages at a time. Way faster to find something on a 4k monitor than on a full HD one. On 4k, you see 4 times as many information at once.
For this kind of work, you don't need high brightness, 400 nits is enough. My vp2290b has 235 cd/m^2 brightness, which is actually low, but it looks awesome. It has 8 CCFLs, you know. Only 24Hz refresh rate now, can do 48. But I love it, it's a heavy duty worker. Needs two DVI-I cables (or four DVI-I for 48Hz).
So, I'm looking forward towards 3:2 aspect ratio monitors for professionals. Hopefully even smaller diameter ones, because when working with a CAD, you want the dots to be so small, that you don't see they're rectangular. You don't want to see jagged lines. This monitor, being 24'' would be perfect. At 32'', it's a little bit too big for me.
The other group I can think of are programmers, they barely see 100 lines on the contemporary 16:9 aspect ratio monitor at one.
When the wide aspect ratio happened, it ate 1/4 of our 4/3 monitor estate, so to speak. Yes, in a notebook, limited by horizontal width, you can have 33% more space on a LCD with 4:3 aspect ratio than with 16:9 aspect ratio.
Go figure yourself, how much screen estate was eaten by the "widescreen" revolution. See
https://commons.wikimedia.org/wiki/.../media/File:Aspect_Ratios_and_Resolutions.svg