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This is one of those things that,at least in the vacuum tube days of TV, manufacturers thought they could bypass and save a few cents on. Once TVs became solid state, adding DC restoration became much cheaper.
Another area that was scrimped on in Vacuum tube TVs was the sound system. The use of ratio detectors/quadrature grid circuits without adding a true limiter stage is one of the reason tube type tvs have so much trouble with buzz in the sound.
For example, I have two Hoffman Easy Vision TVs, one a 1953 Mark V chassis and one a 1954 chassis. The 1953 Mark V taps the sound off of the video detector and has two sound if stages, one being a true limiter. Sound is great. The 1954 model is cheapened with the sound being taken off of the video output and only one non-limiter IF stage used. So far, I have not been able to completely eliminate the buzz from the sound. A complete re-alignment might help(but also might not). The 1954 is also cheapened in the IF circuit(no issue using a DTV converter to drive it) and in the sync circuit(possible issue with strong signal). Both use ratio detectors for the sound.
Moral of the story-manufacturers are always trying to reduce cost to make more money. Make the product just good enough to match competitors.
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