TV engineers' problem is locking a picture to another picture to allow them to be cut without glitches. This requires timing video signal one to another very accurately. If the signals are not timed within a vertical frame, you see a roll on a cut.This requires an accuracy of one vertical line, about 1 part in 600. To prevent a horizontal shift on a cut, you need a lot finer accuracy, about 1 part in 250,000. Doing this with valve technology in the 40s was impressive work, but it did require devoting over a third of the video bandwidth to synchronisation pulses.
To prevent a colour shift in composite video, you need to preserve colour phase, which means you need to be locked to a fraction of the 4.3 MHz colour signal. To do this, every playback device in the professional broadcast world is locked to 'station sync' which is driven from a very tightly-locked crystal signal.
When I worked at the BBC, I saw the Rubidium clock at TV Centre that drove the station sync pulse generator, and hence every camera and video tape machine in the building, and on out to the microwave towers and transmission masts, and through the ether to the millions of TV sets across the British Isles, all of their electron guns sweeping across the phosphor dots together as one, beating in time with this central heartbeat.
How could they give up all that order for the chaos of the net?