alt Hacker NewsPiggdekk in Norway are equivalent to North American studded tires. When I lived in the northern parts of the U.S., I had a set of these for times around freezing rains.
Beyond the questions of winter weather properties, there are adjacent tradeoffs between the tire types (outside of studded):
1. Fuel economy
2. Noise
3. Degree of particulate pollution emission
I'm sure that the all-season tires probably have some negative tradeoffs in these regards to, which yields a choose the most optimal product for the time of year. All-season tires to me seem like a convenience food for places where the weather can be legitimately bad.
One other difference that is hard to articulate to North American drivers with respect to understanding Scandinavia and roads: there are places where snow and ice will literally not be removed (maybe not even removeable) from the road when plowed (I presume until spring melt). It just becomes a thick ice pack over the course of weeks. I never encountered any roads in my life (including Northern Minnesota) that were this inclement. North American roads tend to be cleared (plowing or melting) to asphalt or pavement.
All-season tires aren't simply a matter of convenience, they offer a safety benefit. If you aren't driving at normal highway speeds, even if it's the dead of winter and the air is below freezing, your tires will heat up and the winter tires won't have as much traction. The disadvantage on dry roads can be several times what the advantage was on contaminated roads, including during the winter.