What do you do after you've stopped it? Now you have a parked car, you don't have the ability to drive it away. (If you did, you would have skipped the faraday cage net.)

So you need a tow truck to actually take the car into your control where you can do with it what you will (sell it, etc.). But if you had a tow truck, you could just steal any parked car, so how is the self-driving car worse off?