CosmicVoyager said:
...In other words, there is a mechanism inside the ball, which we could develop a mathematical model for that would predict observations, but because a model already exists that predicts without a complete description of all structure, they have no interest in doing so. That is sufficient for practical applications, but people want to fully understand the structure of the universe.
CosmicVoyager, while I certainly appreciate the concept DaleSpam has communicated to us, I really seriously tried to present a picture of a mechanism ("inside the ball") resulting in a limiting value for the speed of an object. I really presented this picture as a serious candidate for answering the question, "Why does speed have a limiting speed, namely the speed of light?" I'll present the graphics again because I think it is a reasonable picture of the situation. I could explain this in more detail, but it would take an unreasonable amount of space here. The picture should not be dismissed as just graphics.
To appreciate the picture a person of course is going to have to develop some concept of a 4-dimensional universe and be able to interpret a spacetime diagram in that context. I can do a tutorial in a different thread if need be (or folks can google "spacetime diagram"). My diagrams are intended to be fairly literal picture models of observers moving at relativistic speeds and "living" in a squence of 3-D cross-sections of a 4-D universe. If one really wants to pursue your "why" question, they should first pursue an understanding of spacetime diagrams if they do not already have a grasp of special relativity.
First of all, just this one fact alone, namely that the X1 axis rotates symmetrically toward the X4 axis for increasing speeds, is adequate to explain why all observers measure the same speed for light. You should be able to see directly in all of the pictures below of different observers with different velocities that the ratio of X1 to X4 is the same for each one of those pictures. This is a definite answer to the question about same light speed for all observers. (It's as good a "Why" answer as you would get about the blue sky.)
Again, the sequence of 4-D pictures below (X2 and X3 supressed) are a serious attempt at demonstrating why there must be a limiting speed. Once understanding this, an even more burning question of physical reality arises: WHY does an observer's 3-D cross-section view (the X1 axis) of the 4-D universe continually rotate so as to eventually converge on the 4th dimension (X4 axis)? This seems to be the more fundamental question, because again, that magical rotation leads to the limiting value (X1 and X4 axes converging in the limit).
In other words, if the model below, as implied by special relativity, is accepted as a working model, we could then proceed to the next "why" question: "Why does the X1 axis rotate?" (Note that in Newton's model of the universe, the X1 axis never rotates--but then experiments have shown that Newton's model does not work at relativistic speeds).