Because you won't have to remove the morph from each separate body part. What was happening to me was that, using Poser's Morphing Tool, even though I was only morphing the chest area, the morph would always spam 90 body parts. And it was a pain to remove them one by one using the parameters palette.

I also tried that MorphRemove script IsaoShi posted up there, but it leaves blocks of settings about the morph inside the PZ3 file, even though it removes the delta information.