Does anyone know why manufactures don't make 34,36 inch 4k monitors? There are plenty of 32 inch 4k monitors but next 4k resolution is 42-43 inch. Nothing in-between. The whole segment of 32-40 inch monitor is dominated by ultra wide monitors.
The most common size is 34" . They are the same height as a 16:9 27" and the same amount of vertical pixels - one of 1080,1440, 2160. It is derived from the same panel as what goes into a 27", just longer.
The next common size is 38" @ 3840x1600 . I haven't done the math, but these are presumably derived from 16:9 42" 3840x2160 panels, with the bottom 560 pixels cut off.
I'm not aware of any '32" 16:9 but longer' ultrawide yet, but they will likely happen at some point.
I think you are right that there's nothing readily available between 32" and 42", but ultrawide do not contradict that UW panels are a niche product line so they use existing panel PPI arrangements.