They do test in snow areas. Just many fewer of them and with no successful feasible solution. Notice that the road in the video is cleared of snow. The problem

They do test in snow areas. Just many fewer of them and with no successful feasible solution. Notice that the road in the video is cleared of snow. The problem is when the road is covered with snow. This is a very common occurance. So far it requires solutions like pre-existing ground penetrating radar mapping of all roads or some not invented yet solution. There's a team at a Michigan university doing this.