here's my take on the subject....
the snowplow is a fundamental part of skiing...you have to have a solid snowplow to be a good skier. Although technically it shouldn't happen with the correct use of todays ski technology, for a split second you will find a snowplow like position in the the transition of many a strong skiers turns. Therefore it is a natural ( and probably the easiest ) position to resort to when trying to shave off speed or make small direction adjustments.
That being said I do it all the time to shave speed etc. on rails and jumps, but I would like to get out of that habit and use a more "parallel" technique because I think it looks much smoother. I find Nick Miles from montage to be a great example of someone who looks to be in complete control as they are rolling into a jump or rail. If we care so much about style in the air not to mention "afterbang" why shouldnt we care about style inbetween features?