Well, the point is permanent removal either through brain death, physical death, or the death of the soul. Likewise, since Soul is no longer simply the stat that powers masteries, if you goto zero Soul you will pass out as well, same as with mind.
This gives everyone a chance at a weakness for a while. Big strong power characters get sapped with Soul Drain and they are out! Powerful Magi gets Pshycic Blasted with a good shot… night night. Etc.