"Viewing television is a very different activity from listening to sound broadcasts. The radio set can remain on for hours at a time; you can enjoy it as background to reading, writing, homework, housework (some people can even enjoy it as background to conversation, darts, or bridge). The television set demands your attention; you cannot enjoy television from the next room.From the BBC Year book 1946 via a new (to me) media history site, Transdiffusion.org.. Also contains various other fascinating pre 1950s broadcasting docs.
You must sit facing the set, with the lights down or shaded, and if you are a normal viewer you will find yourself very reluctant to be disturbed during a programme that you enjoy. This puts a limit on the hours that the ordinary viewer can give to his viewing. Broadcasting must go on from morning till midnight, but television is quite another matter, as most viewers will soon find."