I don't know if this is accurate but I recall an article that said another significant difference between western WA snow and snow in the states that get seriously cold for a long time in winter is that the ground in western WA usually doesn't freeze like it does in the colder states.

When snow falls in western WA, the fall at the start gets melted by the ground, and the refreezes as the following fall hits it. This results in an ice layer covered in snow.

The states with frozen ground don't get that bottom layer of snow melting, giving them just ground covered by snow which is not as challenging to drive on as snow on ice.

So what we get in western Washington is that when it snows it gives us a particularly annoying kind of snow for driving. Combine that with us not getting snow frequently enough to get good at snow driving even in regular snow, and driving is a mess when it snows here.