It's a quick & dirty way to get improvement up to a low performance ceiling. For the instructors who confuse stability with balance, or those who want something quick for the client, it works. Dead-end move, of course, but for lowest-common-denominator ski instruction for anybody with any boot fit, any equipment, any degree of fitness & balancing ability, etc., it offers some perceived improvement.
If you get a student that has all of these I'm sure it is a great experience for both the student and the isntructor, but what do you do so that you can deal with the other end of the spectrum? Does the instruction change - meaning do you completely reverse what you might normally teach (this was taken from the "two footed stance" thread - would you advocate 50/50 weight distribution where you would normally advocate independent leg action with a strong inside half, etc.)? If you compared the lesson that the two students received - who would get the better lesson in terms of making them a better skier?