Can you show me where it says how many thousands of crews had no problem
After any accident/incident/close call you can point to thousands, if not millions, of prior successful operations, but following a failure you learn from the lesson imparted and endeavor to do something about it. 747 that had the slats retract at rotation not so long ago, never a problem prior, would you expect the authorities to do something about it, or dismiss it, as it's never happened before? The question is why did it take 16 of the 44 total occurrences before it was made an issue, anyone of those events could have had the possibility of metal and bodies strewn across the landscape.