Caporegime
The position of the bar on the back doesn't lend itself to getting depth. You always need to keep the bar over your feet during the movement.Sorry to butt in but, eh? Confused.
Take a look at this pic.
![squat-variants.jpg](http://crossfitmtolympus.com/wp-content/uploads/2011/06/squat-variants.jpg)
with the low bar squat you have much steeper back angle. If you imagine the person in the image going lower than they are the first thing that happens is the butt tucks under or your chest drops really low.
High bar and front squat are better for depth.