Probably because most techies live in sunny and warm California, this has not yet been a priority:

“The complexity of winter weather is going to take an incredible amount of work for automation technology to tackle,” says Bryan Reimer, a research scientist at MIT specializing in autonomous driving. “Ice-weather conditions are incredibly difficult.”

Source: Snow and Ice Pose a Vexing Obstacle for Self-Driving Cars | WIRED

There has been a “sunny and warm” bias in much of the “techie” part of the auto industry. Most EVs – so far – are not designed for winter snow driving (versus, say, AWD SUVs). All EVs have no spare tire, which is sort of okay when you live in populated areas, but not good when living in areas without cell service and dozens of miles – even 100 miles – to the nearest service station. Part of the bias, of course, is solving the easier problems first. The last 20% is hard.