A lot of these "accepted wisdom" things you see I trace back to what the burgueoise did 100-150 years ago.

The crib thing was because the rich didnt want to be woken when the nanny cares for their child at night.

Same thing with sleeping for eight hours at once. It was what the rich were doing as they built the industrial revolution, and demanded it of their workers. Soon doctors got on board and ridiculed those that slept the old way.