Nursing Birth also has an excellent post on the subject.
All these posts and the "pit to distress" subject keeps making me think of the quote that opens Henci Goer's Obstetric Myths vs. Research Realities book: "Facts can be disproved, and theories based on them will yield in time to rational arguments and proof that they don't work. But myth has its own furious, inherent reason-to-be because it is tied to desire. Prove it false a hundred times, and it will still endure because it is true as an expression of feeling...It is illogical--or at least, pre-logical; but from this very fact it gains a certain strength: logic may disprove it, but it will not kill it."
This, to me, explains the essence of why harmful maternity care practices continue to persist in hospital settings.