Comment by adrian_b

I disagree about "Illuminated objects (natural or manmade) almost never go outside that".

There are plenty of frequently seen purple-red-orange-yellow objects, like flowers and fruits or clothes which look very noticeably washed out when seen on an sRGB monitor in comparison with being seen on a DCI-P3 monitor, where they look pretty much like in the original (assuming adequate software configuration for managing the color spaces).

While for commercial movies I cannot verify the fidelity of the color reproduction, because I do not have access to the original images, for photographs that I am taking myself there can be no doubt that the color gamut of sRGB or Rec. BT.1886 cannot reproduce satisfactorily a lot of commonly used things.

The primary red of sRGB/Rec. BT.1886 is really a very bad red, very far from a monochromatic red, because the red phosphors of the early CRT tubes could have either good saturation or good luminosity, but not both, so they have chosen a low-saturation red that was bright enough to match the green and blue phosphors.