There are similarities between knife sharpening and razor honing and there are differences as well. I think the main difference is that with a razor, you are trying to get the edge both keen and smooth. With a knife, keenness is usually more important than smoothness. If fact, for some tasks like cutting nylon rope, a slightly jagged knife edge might work more efficiently than a razor. After all, we do have serrated knives, but not serrated straight razors.