The thing is, the old protocols all have their limitations.
Analog audio - unless it's balanced - is highly vulnerable to all sorts of external interference. S/PDIF is normally two channels of PCM audio (that's decently easy), but it can carry up to 8 channels of variously compressed audio and not every sink or source supports all possible codecs (thanks to software patent licensing BS). In either case, 48 kHz sample rate and 20 bits precision are the fundamental limits.
For video... analog maps well to CRT displays but reconstructing signals from analog inputs in a TFT/LED screen is inherently a lossy process, and running anything more than 1080p is a gamble and requires good, short cables. And digital video at higher data rates becomes a nasty mess and practically devolves into RF black wizardry at the kind of stuff you can pull off with modern digital video signalling - 4K @ 240 Hz refresh rate, this is utter insanity if you just think how much data is being shovelled around.