Succinctly put, stances are a fundamental and foundational part of American Kenpo. From a specific point of view, stances may be perceived as the maximization of stability, mobility, and availability. Stability being defined as the ability to maintain one's balance and space under optimal and adverse conditions; mobility being defined as the ability to maneuver quickly and without self-imposed impediments; and availability being defined as the ability to effectively use the natural weapons on your body. And, although there is a fourth and very important element to the overall discussion of stances, visibility, it will be purposely excluded from this overview.
Stability, in American Kenpo, is so important it is even given a rule for self-defense: "Always obtain (create) a stable base." This rule is so important that it is often referred to as rule #1. But what is not mentioned, and for the most part, not discussed, in this rule are the implied parts of this equation. In this case; mobility and availability. While it is extremely important to create a stable base (and this is not a criticism of this rule), it is also critical to maintain (or create) mobility, while simultaneously maintaining the availability of as many weapons as practically possible. In the context of body and foot maneuvers, these concepts should be considered inexorably intertwined. In other words, if at all possible and practical, one should always try to maximize for each, and attempt not to favor one (1) or two (2) at the expense of the others.
One of the main reasons why these other parts of the equation are frequently left out of consideration is because our base Kenpo stance, the neutral bow, by design is intended to be simultaneously stable, mobile, and leave availability of all four (4) of our main natural weapons. This is why the alignments (heel-knee / toe-heel) of the stance are so important and are defined with those specific parameters. One (1) way to think about alignments is that improper alignments can lead to improper stability, but may also lead to hindered mobility and availability; thus, potentially compromising one's defensive and/or offensive capabilities.
Looked at from the perspective of not optimizing each concept together; by not maintaining proper alignments one may maximize for stability, but may simultaneously compromise mobility and/or availability. For example, if one were to obtain an extremely deep neutral bow stance, they would be very stable in relation to a front-to-back orientation. Any pressure from the front could be withstood better than if in a much narrower stance. Yet, mobility and availability in such a rooted stance would be compromised, potentially to a severe extent. And, although some of the alignments are still maintained (in this case width and height); the alignment of depth was compromised, and therefore mobility and availability are diminished. In this scenario, one (1) of the elements is emphasized, but at the expense of the other two (2).
And, the converse is also an example to consider. Standing in a very narrow neutral bow promotes a high degree of mobility and availability, but at the expense of stability. Again, the alignment of depth is compromised in the opposite direction. Therefore, that same pressure from straight ahead now might not be able to be withstood. Yet, the ability to move because of that pressure would be greatly increased; and the availability of the major weapons is also maintained. In this scenario, two (2) of the elements are emphasized, but still at the expense of one (1) of the elements.
In an effort to rectify these issues and to optimize for all three (3) attributes at the same time, a balance must be struck. In short, one could simply adhere to the defined alignments for this stance. They are the default alignments for a reason. To state that reason explicitly: all three (3) of the elements can be optimized for simultaneously, and therefore should be in the most situations.
In specialized circumstances, one might want to optimize completely for stability, or maximize totally for mobility, or even availability. But in the vast majority of cases, optimizing for each attribute simultaneously is a better strategy; especially when in a combative situation. On the other hand, in non-combative situations each of these factors may or may not be of high consideration; particularly within learning and/or analytical environments. Because of this, this discussion should be considered heavily weighted toward combative scenarios.
Furthermore, one should understand that American Kenpo stances purposely omit the arms, hands, and head as part of a stance. And, to some small degree, the upper body and legs. These elements primarily fall into body maneuvering (potentially using the upper body and legs), not foot maneuvering (obtaining stances) and stances (the stance itself). And, although these elements are not part of stances themselves, they are part of the equation (Rule #1) mentioned above (for example: other defensive/offensive considerations). But these other factors are beyond the scope of this specific analysis and therefore will not be covered here.
Finally, in relation to Long Form Three, one of the reasons why the form is not as flowery as it could be is because of its theme stance - the horse stance. The horse stance is the primary training stance, where the neutral bow is considered a secondary training stance (but the primary defense/offense stance). Yet, one of the main reasons the horse stance was chosen as the primary training stance is not for mobility, stability, or availability, but due to its similarity to our natural stance (along with its simplicity and ability to also workout the legs). Coincidentally (and this should be considered within one's analysis of Long Form Three), the horse stance is specifically not optimized for stability from the front, but rather to the flank (side). And, the form demonstrates its use in both of these scenarios. Due to these characteristics of the stance and its copious use within the form, the execution of the form is left with a less than smooth feeling when compared to its shorter version (Short Form Three).