It looks like cost engineering was already happening back in the 1930s:
In the foreground, the destroyed original power transformer from the 1939 Zenith 7-S-363 radio; the rear, an equivalently rated replacement built in October 2010 by Edcor Transformer. In order to squeeze out a few cents cost savings per chassis, Zenith under-rated their power transformers and ran them right at the limit. In certain modes of tube failure, or just age and components wearing out, the power transformer’s razor-thin safety margin would be exceeded resulting in overheating, shorting and melting. Which is exactly what’s happened on the one I’m repairing at some point in its life.