I completely understand your preference for 16:10 monitors, they do offer a bit more vertical space which is really useful for working. The reason they're so rare now is because the industry shifted towards 16:9 due to the demand for widescreen formats in the entertainment industry, like movies and gaming. As a result, manufacturers started producing more 16:9 monitors to cater to this demand, and 16:10 kind of fell by the wayside. It's a shame, because like you said, they're really great for productivity, but you can still find some niche or professional-grade monitors that offer 16:10 aspect ratios if you're willing to look around.