The dog has a degree of autonomy or self-agency, and can make decisions that put its owner at legal risk. Someone else brought it into the world, but you, ultimately, made the purchase.
You made it yours, the problem’s on you.
Dog owners have physical and (some) psychological control over their dogs. Not true of SDCs.
Dogs are not programmed, they're bred.
Even very dangerous dogs can be kept in a way that renders them unable to harm anyone. Not true of a car that must drive around in public.
No breeder guarantees a dog's behavior for its lifetime. SDC manufacturers will guarantee the car's ability to drive.
Continuing the counter argument: who is liable if the phone you bought with faulty battery explodes causing life and property damage?