32" is large enough that you can get away with 100% scaling and have much more actual workspace instead of increased clarity. It's not really until you get to the 15" or 17" laptops 4k starts being about high DPI and in that space the MacBook Pro screens actually overshoot the target a bit.
Because most people pick monitors by size, not resolution and PPI.
4K is also popular because it fit within the capabilities of common HDMI and DisplayPort ports on people’s computers and cables.
If you try to sell a monitor that doesn’t work well out of the box with the average laptop, it’s going to have an extremely high return rate. That’s why display resolution will always lag behind the common capabilities of your average HDMI port on a cheap laptop.
I had one, Dell's UP2414Q. It was a piece of shit, mostly due to requiring multi-stream transport to run in 60 hz mode. So you'd get a GPU driver or OS update and the screen would stop working. Sometimes the panel would split in half and one of them would black out or shift its content sideways so there was a seam in the middle and a piece of the edge wrapped around to the center. Would not recommend.
The ones afterward that got rid of the MST requirement might've been better. Pixel density was great.