I think the reason would more to be with the fact that premier made and sold a lot of tenor drums, and more to the point, marching snare drums in that size. Its ecconomical to employ that size thus in their drumsets.

I haven't had my hands on as many Premier marching drums as other brands, but have been around marching drums more than most folks and the vast majority of 14" drums I've seen are 10" or 12" in depth. I don't know if I've ever seen one in the 8" or 9" range.