[timmy]

Originally Posted by old_tv_nut

Multiple reasons.

1) The picture tube primary colors (phosphors) were changed over time from the original NTSC standards to get brighter pictures (the green saw the largest changes, but blue changed significantly also. The red changed slightly; the strongest change was toward orange in the all-sulfide tubes.
2) TV manufacturers made proprietary changes to the color circuits to partially compensate for the phosphor changes
3) TVs for a long time used a quite cyan white balance, to reduce the load on the red electron gun, due to the relative inefficiency of red phospors
4) meanwhile, TV cameras were designed to make good pictures with the newer phosphors, so there were two rather uncontrolled adjustments in the system, at the camera and in the receiver.

5) Finally! PAL and HDTV settled on the correct circuitry in cameras and receivers for the new phosphors, which also became the sRGB standard for computer images (jpg files).

Interesting , lots of changes just for tv.