Basically, it is used because of the shorter ROM. That's it.
The technicalities of the variation is that you have greater forward lean and more stress on the Glutes and hip muscles than the Quads. For some, this means a big increase in their Squat numbers.
For others (like myself) the variation is not preferred. I found a wide-stance PLing style Squat to put too much strain on my lower back; decreasing the amount of Squatting I could do on a given day. In addition, my poundages were actually greater when Squatting with a narrower stance (my stance is usually shoulder width or slightly wider). I am also of the belief, perhaps unfounded, that a narrower stance will give me better carry-over to my pulls.
I'm thinking that it's up to each lifter to decide which stance is better for him.
Form follows function.