“All season” really means “all seasons except winter.”
With the improvements made in recent years to all-wheel-drive systems, vehicles equipped with them no longer suffer nearly so much in terms of cost and fuel economy. Those vehicles have therefore become hugely popular in areas that see a lot of unfavorable weather in the winter. That makes sense, as they do offer an advantage, but there has always been a better (and generally cheaper) option for dealing with winter: snow tires.
The following demonstrates just how much a difference a good set of winter tires can make. Amazing how frequently people forget this.