As someone who uses the pipe rubbers, I do so mostly for reasons of comfort. I am not a serious clencher, usually holding it in my teeth between puffs while my hands are busy. What this means is that I think it would take me a long time to indent a vulcanite stem to my teeth, and make it more comfortable. I like the grip and softness of the rubber bits. I also prefer acrylic stems which can be harder. There are certain pipes the rubber bits don't work well with, my Ropp Vintage with the horn stem is an example, so I just go commando on that one. The horn is actually a very forgiving and comfortable material.
That said, it is hardly a disadvantage that my pipe stems are often free of tooth marks. I have never sold or traded in a pipe, as I buy them to smoke hard, but maybe one day I will want to...
Anyway, I don't think there is a wrong way to approach this. I am actually pretty jealous of those who can clench through an entire bowl while doing all sorts of other tasks.