It's too easy for display manufacturers to compete on moar pixels, moar fps, moar refresh. You just try to embiggen your numbers compared to your competitor.

Meanwhile, features where you can't compete on numbers but can ruin the experience are ignored.

What are these features that can't be measured?

Plenty of people who test monitors also compare things like color coverage, brightness, latency, contrast, viewing angles, etc, etc, etc. If you mean the entire monitor, they generally also cover things like how the display swivels/mounts among other things.