I try not to and use mat files, but then you have to explain that they are in the mat folder. I think maybe the character packs are keeping that option alive as they are nearly always in the pose folder along with the morphs, maybe it's easier to keep them in one place.  I tend to take the best skin option of a char pack, add EZSkin  and resave in the mat folder. 

I think there needs to be a campain going to encourage the use if there isnt a reason why it should not, lol :)

Tools:- Win10, Dell XPS8900, ZBrush, Marvelous Designer 11, Hex 2, PSP8. PSP 2019 Ultimate, DAZ Studio, Affinity Photo, Affinity Designer, Filterforge 11, flowscape,  Classic UVMapper, and several headache tablets.