Why Are Traffic Controllers Rude?

Here is a book waiting to be written.  'Hints, Euphemisms and Thoughtful Metaphors For Air Traffic Controllers.'  This would give tips to the people who make sure that aircraft take off and land safely to make sure that while they are doing it, they do it with good manners, politeness and decorum and show a polished and cultured face to the world.
It is interesting to think why nobody has written this book.  When lives are at stake, as they are whenever hundreds of people cram themselves into a thin metal tube full of highly flammable liquid thousands of feet in the air, we don't expect people to communicate politely.  We expect them to communicate clearly.  Very clearly.

Interestingly, there has been more than one fatal air crash where the problem was afterwards revealed to be poor communication between the air and the ground crews.  This is not always simple misunderstanding either.  Sometimes the air crews have positively shrunk from saying what they think out of fear of appearing rude.

So being too polite can kill you.   Obviously everyday life isn't like flying, but I wonder if we sometimes don't realise the downside of not speaking clearly about what we want.