{{Nlpnt}}-"Economic forces being what they were, advertisements were almost always for consumable products (that is, automakers and long distance carriers need not apply), "

Um,
* "..need not apply" implies discrimination (against ''paying''sponsors?) "Were not interested" would make the point more accurately.
* Many automakers ''did'' sponsor Golden Age radio shows (Fred Allen and Ford comes to mind).
* There wasn't competition between long distance carriers in the United States until 1983. [=AT&T=] didn't ''need'' to advertise (they did in print however)

I left this up for now because it's a good example of ''something'' (what's that trope called?) simply because of my third point (WeirdAlEffect? AluminumChristmasTrees?)