Considering most of the U.S. (primary market for self-driving cars) experiences snow and ice several months of the year, why wouldn't engineers spend time to ma

Considering most of the U.S. (primary market for self-driving cars) experiences snow and ice several months of the year, why wouldn't engineers spend time to make this work well? Is there something inherent about adverse weather that makes humans better at it? The evidence is that anti-lock brakes and variable traction controls have lead to a reduction in crashes in adverse weather conditions. Driving in snow and ice is hard. Why wouldn't a system that can make much finer and frequent adjustments outperform people? The only thing that is really holding back self-driving systems is the computer vision aspect, which is mitigated with Lidar and by further research into computer vision improvements.