Here it is from an outsider's point of view.
Skiing fast is fun. Skiing fast is easy. Skiing slow on a steep slope by forcing my skis into tight little circles is hard work. I don't want to fight against gravity all the way down the hill; I want it to carry me away effortlessly; I want to be free; I want to let her rip.
Most people want to have fun. Most people don't want to work too hard. They generally don't have a lot of practice making teeny-weeny circles on steep pitches; they have spent their time having fun.
The Examiner has had lots of practice and probably was making the tightest, teeniest circles he could; maybe he had teeny-weeny-circle-making skis. He probably uses his little turns to ski the fast line slow just like a skateboarder uses sideslipping down the hill. He probably gives his ego a boost with how well he can do it. He may have deliberately set a task that was at the limits of his own abilities to test the abilities of his students.
So in essence the skiers had spent more time perfecting fast skiing and not as much time perfecting slow skiing. Should they have spent more time perfecting slow skiing?
Probably not. I'm sure they were all quite capable of slamming on their brakes if they really needed to slow down. The skill they failed to demonstrate was clearly not one they had found useful in thier skiing.
The fact of an examiner setting a hard task for his students brought to light another question. "Is fast skiing desirable in recreational skiers? "
The answer is a resounding "Yes!" Control and power and especially control of power are what draws many people to this sport. Without fast skiing there would be no adventure, the sport would appeal much less to the instincts of many who partake in it.
Too-fast skiing is another story.
So the question is "What's too fast?"
Recreational skiers should ski as fast as they want to so long as they are still in control. That is they should be able to avoid obstacles and other skiers. They should slow down at trail mergings and blind spots. However when they have a clear field of view and nobody in the way they should be able to let gravity have her way.