alt Hacker NewsI wonder if it's a carryover of an old regulation that used to make sense. Modern all-season tires are better in snow than the best winter tires were several decades ago.
Also, you need studs or chains to get traction on ice. The difference between a winter tire and a summer tire is the temperature range where the rubber stays flexible. When the rubber gets hard, it will keep its shape instead of complying with the surface of the road, so it loses traction quicker. Ice is flat, so there's no difference between tire types, and there's nothing to grip on to.
Nordic studless winter tires (different from Central European winter tires so also probably different from whatever you get in the US) do give some grip on ice, while all-seasons can be nearly as bad as summer tires. https://link.springer.com/chapter/10.1007/978-3-031-66968-2_...
The government has done ongoing research on these subjects and the regulations do get renewed (e.g. some properly rated all-seasons are now allowed)