About 99% of builders don't use Graphite because it's not the kind of protection that most builders desire. If you hit a rock, Graphite will do nothing. If you drag your boat up a smooth sandy beach, scientific testing may prove that Graphite is a better surface than varnish. You can repaint on a coat and black is black so it's not noticable. Most builders want a clear coat. Because Graphite is used as a lubricant on some metal to metal surfaces in industry, it's assumed that you are going to slide over abrasion. To an extremely stretched extent it might be true. But for abrasion resistance, epoxy is harder, clear and it's already on the bottom, so people have great success with that. And.. you can re-varnish the bottom of your boat whenever you want as well. Graphite and epoxy mix is no magic lubricant that's going to help you slide over anything practical that an epoxy with varnish won't do. Otherwise, everyone would be doing it. Graphite is a nice coloring agent if you want black.