Because, no matter what, the ability of the human being to get himself into a bad situation is (or ought to be, legendary). Take the automobile, if Jo Bloggs were taught to control a car at high (Motorway) speed, or in an emergency braking (once every 4.5 months on average). The Jo bloggs would be less of an accident statistic. Flying is in short dangerous. We MUST take every oportunity to cover EVERY eventuality that may occur in the air. It's no good saying that if you don't this, X will happen, here's how to deal with X. When if you DON'T do this,then Y will happen, Y is very bad, soooooo bad in fact we daren't teach yo how to deal with it' because it's tooo dangerous.
Good enough???