This implies that walking has a hard limit on desirability, which is easily topped by driving, even with the worst traffic. You have to make driving worse to tip the preference toward walking, even if the conditions simultaneously make walking less desirable.

If driving 5 miles is likely to put your car in a ditch, you may opt for a 200m walk, which may only plant your ass on the concrete once or twice. If you have to shovel snow for 20 minutes to drive anywhere at all, you may prefer to just pull on some wellies and hoof it through the drifts. If every mile you drive is rusting away your vehicle's underbody due to road salt, you may prefer to wear away your boot soles instead.

If you could wave a magic wand to install a roof over ever road and highway, the residents would squeal with glee, toss out their tire chains, shovels, and boots, and get right back into their cars.