Ever seen a downhill racer needing to poleplant when hauling ass down the Hannenkahm at Kitzbuel? Of course not, because they don't poleplant in downhill. However they still use poles when they race because they are better, faster, and more balanced by using them. If you made Bode ski a downhill course without poles he would still get down, but he would be slightly slower, because he would be that much less balanced in the tricky spots. Even the lightest drag of a pole on the snow beside you is a micro-balance adjustment that is not available to you without poles.
There's no question that Andy and the boys can shred some sweet stuff without poles, but you won't see them taking a Hugo Harrison line without poles.
Take away Dale Begg-Smith's poles, and he'll still get down the world cup mogul course, but not as well as does with poles. Dumont and Tanner could still do a sick pipe run without poles, but not as good as they can with poles.
You can ski down the hill with your boots completely undone, and as a training exercise it will help develop balance, co-ordination etc. However that doesn't mean that it is better than skiing with your boots done up. We don't "need" to buckle our boots, we're just better skiers when we do.
As a training and skill development exercise, skiing without poles is good for your skiing, because it takes away some of your ability to re-adjust your balance and will force you to be more balanced overall. (Same goes for skiing with your boots undone.) However when you are in a position when you want to be able to ski your absolute best, using poles is a definite advantage.
I have nothing against anyone who prefers to ski without poles, do what you want and enjoy yourself. However, the reality is, not using poles is a (slight) handicap to your overall skiing ability. Of course we don't "need" to use poles, we're just better overall skiers when we do.