I train in Taekwon-do (1st Dan Instructor) and Ninjitzu (Beginner) and I had an interesting insight/question arise from my Ninjitzu Instructor (which is why I picked up the second art):
In Ninjitzu's Shizen (almost like TKD's Outer Open Stance, so a 50/50 weight distribution per LEG), we are supposed to bear ~2/3rds+ of our weight on the ball of the foot, and only ~1/3rd on the heal. This is to produce a more assertive stance that is more agile as well as better able to better absorb a hit from the front.
For me, this made a lot of sense as in Ice Hockey if you are caught on your heals you end up on your butt. Plus the shape of the human foot; a long-ish forward platform (the tarsals + metatarsals) with a rounded back that does not extend to the rear (the heal). If you are caught with too much weight behind, that rounded heal will dump you over.
Anyway... I brought this question to my Taekwon-do instructors (2nd, 4th and 6th Dans) and it was pretty clear that they had never thought about it in this way either. The question is still open on the TKD side (we are all having a think about it) but they seem to think it's a 50/50 weight distribution across each FOOT (50% heal, 50% ball of foot).
So... what sort of weight distribution across each FOOT do you maintain in your martial art? And for what reason? IE: TKD's L-Stance (aka Back Stance) has a weight distribution of 30% on the front LEG, and 70% on the back LEG, but where do you carry that 70% on the back FOOT?