Why do some systems have lower stances?

Is it possible that lower and deeper stances are also a product of the effort to dampen it down and to create greater physical fitness benefit when pushing for the incorporation of martial systems into the Okinawan/Japanese school systems?

If true, then the other trait supposedly a innovation of the Isshinryu system of natural stances vs. deep stances is also merely a return to original karate or Ti/Te. I just have to ask the questions and express the theory simply because many Isshinryu factions, as other martial systems I suspect, will fervently and furiously refute this theory or assumption since it goes against their supposed belief system.

Even when I have observed systems in sparring/kumite/competition kumite they set in a deep stance yet once the action begins they are up and in a more natural stance. Many do the bouncy bouncy thing wasting energy, etc.

I once read somewhere that Funakoshi Sensei deepened the stances in response to physical fitness, etc. Holding and assuming and keeping deep stances along with moving into and out of them is strenuous, yes?

I guess one needs to evaluate and test all stances both deep set and more naturally set to see the pro's and con's of their use. I suspect much like Marc MacYoung explains in his book that it depends on the technique, the situation, the application, and other more chaotic or constantly shifting situations of fighting. Hmmm, more basics/fundamentals to learn and practice, yes?

One of the benefits of the higher and more natural stances I use in Isshinryu is its allowing me to move in a variety of directions quickly which seems to work well in kumite/sparring sessions in the dojo.

Why, Oh Why, didn't I ask these questions so long ago!