Warming Drawer:
The role of the warming drawer was simple:
Stay-at-home housewives often found their husbands delayed getting home - late train, traffic jam, boss had something on his mind, whatever.
A warming drawer could hold a meal so that Daddy could come home to a hot dinner with the rest of the family; it was considered important then that the family sit down together (it should be considered more important now than it is).
It also made it easy to hold food if you were having guests, making it possible to prepare things ahead and be completely ready when guests arrived.
"Warming drawers" with no elements are actually storage drawers mis-represented by ignorant sellers who don't have a clue what they're talking about.