It is my understanding that Mat and Morph files came into being at the time when the program bug that allows conforming clothing to work was widely publicised and exploited. Since it was a quirk of the pose mechanism that allowed this to work, pose files (or files that looked like pose files to Poser) became the norm for injecting morph settings and applying materials. It has been this way ever since I began using Poser some 9 years ago, so the practice was obviously entrinched at that point in time.

Why continue to do it? Because this is how the rank and file EXPECT it to be done. I readily admit that before I adopted my own organization scheme for Poser content, I seldom thought to look in the materials folder for content. If it wasn't in a mat file in the pose folder, it didn't exist for me.

I suspect that vendors would get considerable pushback from the unwashed masses if they were to stop providing mat files in the pose folder, but can't prove it.

A couple of years ago, I became convinved that there was no reason at all for Poser content to be organized as the program calls for. I have posted in other threads the changes I made and the methods I used to consolidate everything in just two folders: Figure and Pose. Now, I care less where the various components are put by the vendor because I move everything into a folder in the figures library. That way, I don't have to go looking hither and yon for the <fill-in-the-blank> that goes with the figure in question.

And yes, I agree with Shade... Poses are the only thing I leave in my Pose folder. All the other folders are empty.