2. Therefore the costs of adding such a device (certification per aircraft type, required inspections and maintenance (down time plus labor), weight penalty on payload (cash income, fuel expense) have to be less than simply replacing the tires as needed, to actually produce a benefit.
This.
A ten or so HP motor per wheel, heavy, expensive, difficult to maintain, operates in a horrible environment for longevity, really difficult to operationally check pre flight, and consumes lots of power, when electrical power is least in excess. Such a system would require maintenance dependent sprag clutch to disengage the motor, should it seize ('cause you don't want to land with a locked mainwheel - that puts even more rubber on the runway!).