[astrange]

It's probably the onset of modernism - they decided everything in life had to be lived according to logical rules they made up in their heads, rather than just doing whatever folk knowledge your parents passed on that had no rationale. The advantage is this often does work, but the disadvantage is you end up with Victorian parenting, doctors who wouldn't wash their hands because you can't explain why they should, having to eat corn flakes, world wars, etc.