Stances are judged by overall utility - the balance they provide, their stability and flexibility, stances shouldn't belooked at as individual and static parts, each with specific and separate applicants. Stances are only the foundation to a bigger picture. If you film a Martial Arts match, then play it back frame by frame, you can easily understand this principle. Isolate the footwork and you'll probably see many, if not all of the classic stances or variations of them sprinkled among the frame. The in-between frames, the transitions, link the classic stances together. They add freedom and fluidity of movement. If you cut out the transition frames, reassemble the film, and play it again, you'll end up with jerky and awkward motions like movements on some old silent flicks. Splice them back in and again you have to adapt smoothly and rapidly to changing circumstances.

Stances could be looked at as a living thing. In that context, studying individual stances - back, front, side, long, cat stance, horse riding stance, whatever - begins to make a lot of sense. They're great for strengthening your legs, developing balance and even flexibility.