Speed painting in its most "utilitarian" form serves the simple purpose of quickly bring a bunch of models to the gaming table but for me is mostly a study of what is really really essential to make a model/illustration work and look cool;
speed itself becomes more like a nice sub product of this investigation that reveals how simplicity and a few clear key elements are often the best way to create a striking image!
Edit/Ps: here there is also the process for the bases!