If we had a display with n (n>3) pixel colours, say (red, green, cyan, blue) for example, we could display more of the colour space. Shopping list: 4 colour channel display, 4 channel GPU, 4 channel software. Why isn't this a thing already?
1) trying to convince content makers to use new custom high-gamut hardware to capture the new spot colors
2) you'd need a full video content production pipeline that can render to that color space
3) finding enough people to care enough to pay the (substantial) premium for niche production numbers.
4) Most content just doesn't warrant high gamut unless it's narrated by David Attenborough.
So, you have both a chicken and egg problem, and not that big of a TAM to warrant the struggle.