Well, in my particular case, I use an M1 Max MBP with a 2K monitor that I already had when I bought the MacBook.
The problem with 27" 4K monitors is that you can't have integer scaling on them. If you set the scaling factor to 1x, everything will be too small, if you set it to 2x, everything will be huge, and macOS can't properly do fractional scaling because what it actually does is render everything into a 2x framebuffer and downscale that for output.
And besides, only supporting HiDPI displays doesn't mean one can stop striving for pixel perfection. I hate SF Symbols icons because they're sizeless. They're an abhorrent blurry mess on my monitor but they're also not all that sharp on the MacBook screen. If you notice it once, it'll haunt you forever. Sorry. They do look fine-ish on iPhones though because those use OLED displays that lack the notion of a pixel grid anyway.
> Why don’t they produce 5K/6K monitors that allow for 2x integer scaling?
Because 5K panels are probably more expensive to produce than 4K ones, and because that would only benefit Mac users since Windows can do fractional scaling just fine. I'm not sure about that but it might also be that not all GPUs used in PCs can drive monitors larger than 4K.
Even if Windows/Linux do fractional scaling fine, integer scaling is still desirable if it’s an option. Under both I still run into programs that botch fractional scaling some way or another, and given the proclivity of programs on both platforms to be built with oddball UI toolkits I don’t expect that to ever really fully resolve itself.
It’s one of the chief complaints I have with one of my mostly otherwise good x86 laptops. The 1.5x scaling the display needs has been a pain point on multiple occasions.
The problem with 27" 4K monitors is that you can't have integer scaling on them. If you set the scaling factor to 1x, everything will be too small, if you set it to 2x, everything will be huge, and macOS can't properly do fractional scaling because what it actually does is render everything into a 2x framebuffer and downscale that for output.
And besides, only supporting HiDPI displays doesn't mean one can stop striving for pixel perfection. I hate SF Symbols icons because they're sizeless. They're an abhorrent blurry mess on my monitor but they're also not all that sharp on the MacBook screen. If you notice it once, it'll haunt you forever. Sorry. They do look fine-ish on iPhones though because those use OLED displays that lack the notion of a pixel grid anyway.