Low-contrast UIs can work well in a typical office environment on bright screens.
Take your ideally calibrated monitor, and use it as a second screen while watching a movie in your darkened home theater. Now take it and use it outside on a sunny day.
I prefer to adjust the brightness. YMMV.
Your description of sRGB is incorrect. sRGB was specified for CRT screens in 1996, used in an ideal viewing environment that is very dimly lit ("The current proposal assumes an encoding ambient luminance level of 64 lux which is more representative of a dim room in viewing computer generated imagery... While we believe that the typical office or home viewing environment actually has an ambient luminance level around 200 lux, we found it impractical to attempt to account for the resulting large levels of flare that resulted" https://www.w3.org/Graphics/Color/sRGB.html)
That doesn't match my viewing environments, which include the range above.