Originally Posted by RWetmore
??? I don't understand this either.
Do the geometry.
The electron gun has to 'paint' each pixel on the screen, if it has to cover a larger screen than the TV's depth has to grow to a very large size so the same angles can work, or the electron gun has to be capable of rotating a lot faster. (I'm assuming it doesn't actually mechanically move but rather shoots electrons through a pair of plates that just change voltage accordingly, but still you need electronics that are fast enough)
More lines mean a better electron gun is required as it has to be both faster and more precise.
And the screens have to be coated to be able to handle the resolution anyway, so perhaps making a piece of glass that big that can handle that fine of detail is difficult/overly expensive, especially since the tech available to do it came around at the same time as LCD and plasma were taking off.
There's also the problem that you'd need electronics capable of upscaling all input to 1080p, which is still expensive today and would have been wickedly expensive back when companies were still interested in making new CRTs.
PC monitors can get away with supporting multiple resolutions by being multiscan, but typically each new resolution requires image adjustments. The most I've heard of a tv supporting is two different modes with everything else just scaled.