Because people already complain about there being too many files, it's a third again as many VPs to organize, could easily make precedence a living hell, and generally it seems like there's a division between people who can run the main set, and people who can also run adveffects. The only real disputing factor has been DaBrain's medium 3D shockwave in the VPs. (The animated beam glows in 3.6.7 were supposed to be in adveffects from the outset)
If it comes time to add another VP, I'd probably first merge mv_effects and mv_textures (Both have the least performance drain besides mv_core and mv_music, from what I can see), or mv_models and mv_textures (Since many of the high-poly models have their own, more efficient, texture sets based on the versions in mv_textures anyhow)
If people are really determined about maximing their performance->look ratio, they should learn how to use VPView and make their own set of VPs. It's really not that hard and will net them much better results than I could ever achieve.