The Problem is colour depth per channel, an 8-bit display has 256 gradients per channel in RGB 24-bit displays, most TV's will accept 10-bit input, giving 30-bit input, but the display still only handles 256 levels of red, green and blue colour channels. If lets, say there was 16-bit per channel, there would be 65,536 levels of grey per RGB channel, which would create a far deeper colour depth, but would also create a 48-bit colour space, which is way more data per frame of video. This extra channel is just an 8-bit colour depth work around and I don't think it's worth while.