The problem with those tires is that they harden with cold.
Every year the CHP warn people driving Audi or Subaru... to use snow (M+S) tires or chains even when driving a 4WD car,
as many cars get stranded around Lake Tahoe, which makes always big news on local TV.
Here are some comments I found on the Internet:
Truck Chain Requirements | Caltrans
Even though weather conditions may not warrant the use of chains on 4-wheel-drive vehicles at a particular time,
to enter a chain control area, you must have a set of chains (for one drive axle) for your vehicle in your possession.
If conditions worsen or you have trouble controlling your vehicle, you must stop and install the chains.
There are three primary categories of chain restrictions, as shown below:
Requirement 1 (R-1): Chains are required on all vehicles except passenger vehicles and light-duty trucks under 6,000
pounds gross weight and equipped with snow tires on at least two drive wheels.
Chains must be carried by vehicles using snow tires. All vehicles towing trailers must have chains on one drive axle.
Trailers with brakes must have chains on at least one axle.
Requirement 2 (R-2): Chains are required on all vehicles except four-wheel-drive vehicles
under 6,500 pounds gross weight and equipped with snow tires on all four wheels.
Chains for one set of drive wheels must be carried by four wheel-drive vehicles using snow tires.
Requirement 3 (R-3): Chains are required on all vehicles without exception.
Your Subaru, Snow Tires and Chains Explained - All Wheel Drive Auto
Most newer Subaru models just dont have the room for chains, as we have made the braking systems
larger the wheel size has increased to allow for clearance, this also increased the size of the tire.
The chains in some cases will clear the wheel well but could hit the strut assembly, which would cause
the chain to then come loose this is exceptionally true in the rear. The brake line could be torn off,
the abs sensor wiring could be torn out, the chain could hit the body of the car, the chain could do
more damage than I can describe if it was to come loose or partially broken.
As to the issue of a one time use, while I understand its not popular to buy Snow tires,
if chains are not an option what choice do you really have?
Here is a link to a product that may help.