My concern is that by encouraging the practice of doing UX design without touching the surface of a product, we get shitty designs. In a process where UX and UI are seen as separate things the risk is one comes before the other. The UX designer draws the wireframes, the UI designer gets to turn them into pretty pictures, with no back-and-forth between the two. An iterative process can mitigate some of the damage such an artificial division of labour produces, but I think we still start out on the wrong foot. I think a better practice might entail including visual considerations from the very beginning of the design process (as we are sketching).