Originally Posted by
Check Airman
Some people can't / won't do it if it's not explicitly written in the book. I recall a thread here a few years ago about people flying around with the speakers on because the FCOM says to turn it up, but never mentions turning it back down.
That's one reason. Another one is that any manual is a legal document the content of which is likely to be overviewed by the investigating authority in case the brown stuff hits the fan. The legal eagles don't necessarily have a good idea of what is and isn't common sense to a pilot, but they are all very good at analysing text. And what if they find that the contributing system, procedure, maneuver or whatever was not explained in sufficient detail? Hint - think the B737MAX grounding. Or at least a massive claim to the manufacturer. Hence, the manufacturers prefer to sometimes overdo the texts but stay on the safe side.