Around my area having winter tires is a must. A/S is pretty much as good as stranded when a good storm hits. We have mountain pass inspection points/tire chain stops. They check whether vehicles are 4WD/AWD with A/S tires and chains on before they let you pass(this will not happen in the WRX because of the small wheel well). If you have Winter Tires and 4WD/AWD then you're good to go 90% of the time.
Attempt to do the same feat with summer tires is just pure stupidity and attempting the same feat with any A/S tires will get you sent back if you're not already stuck!!!
(Winter tires bears the following snowflake on mountain logo right on the side wall)
I know I maybe starting to sound like a broken record, but the particular requirement above says it all.
Summer Tires A/S tires A/S w/tire chains = Winter tires Winter Tires w/chains
They are necessary for certain places and may not be for others. Non-mountain states may have never heard of such requirements. I guess this is just a proof of A/S (UHP A/S are still all seasons!) being inferior to dedicated Winter tires in extreme winter conditions.