The liability argument is a bizarre diversion. Even the first sentence......if you are the cause of the accident......at that point you are already liable. Period. Driving too fast, poorly, without the right eyeglasses, wrong lane change, red light, two bags of cement in the trunk, nope you are liable if you cause the accident. Your car will be towed away and no one will be inside hanging by their toes looking at the TPMS light. Mine never come on anyway until I have driven for several minutes each day.
So, run winter tires and greatly reduce your chances of causing the accident. And being alive! Buy the TPMS sensors if you do not like tire gauges. DO NOT let the cost of the sensors prevent you from buying winter tire packages!!
I have run winter tires for over 20 years, they are often stunningly better then regular tires.
No, I do not put TPMS sensors in my winter tires, on both the Corolla and the Sienna the light is on during the winter, goes out in the spring.