The point is that if someone runs in front of your car, physics dictates that you can't stop a 1,000+ pound vehicle on a dime. You can lock the brakes up and stop the axle from moving (ABS braking won't actually allow this usually) and the car will still continue forward for some time. In addition many other avoidance strategies won't work. Sure, you could swerve, but what's in your path then?

Machines don't get tired or bored, they don't screw around with the radio or put on eyeliner, or get distracted by text messages. They have other issues but we hope they'll be less prevalent.