If everyone would design against properly calibrated monitors it would be fine, you could just set it to the standard calibration, but they don't so there is no universally good brightness you'd never need to change for. It's like webpage sizes, if everyone built and tested their UIs at the standard physical screen scaling then you would run into a lot less variance in website sizes.
If everyone had calibrated monitors and every app and website was the same brightness, yes.
Instead, it varies wildly, often for good reasons... and then switching windows exposes you to extreme shifts. E.g. switch between photograph editing and a giant white text document, nothing's gonna save you then - stuff that looks correct and good for photography is absurd when most of your screen is the same as the sun.
Calibration is one thing, perceived brightness of the whole screen with specific content is another. And it's heavily influenced by how many nits are available.
Calibration in this case isn't about providing "and so everything then looks like it's the same brightness, because it's calibrated" it's about "and so the same modifications can be applied to everything consistently, because it's all calibrated". I.e. just lowering the brightness a bit below the intended value now is impossible. One thing built on a monitor with it's brightness curve undercalibrated and one with its brightness curve overcalibrated will look two different kinds of wrong when shifted by such a transform. That would not be the case with calibrated sources, everything would shift in the same way and you're able to have it look "wrong" (i.e. darker, capped, brighter, whatever) exactly the way you want, consistently.
Taking it to the DPI example, having things built at a standardised DPI isn't about making everything appear the same physical size it's about making everything tuned against a consistent physical size for the exact same reason, default is always intended and your global adjustments are always consistently resulting in the source material being larger than intended or smaller than intended instead of "well, depends how uncalibrated the source was if it's still smaller or larger than intended".
> Calibration in this case isn't about providing "and so everything then looks like it's the same brightness, because it's calibrated" it's about "and so the same modifications can be applied to everything consistently, because it's all calibrated".
You seem to be assuming the commenter you replied to didn't know that. As I understood it, all they were saying is that advice about calibration is useless for people who don't do photo editing, but whose problem is exactly that different windows have such wildly varying brightness that switching from one to another often makes everything look either pitch dark or third-degree-interrogation light in your eyes.
Which category of people do you think there are more of? My bet is on the latter. They need... Well, if you don't want to call it "another kind of calibration", you're free to come up with another term.
