I think thats the point your missing, it takes time to fully develop systems, plus they have to work within the constraints of the law as it currently stands. Just like driverless cars/busses or lorries, where the systems are in development before the law allows them to be used as intended. You end up with the system only allowed to do a limited amount until everyone is convinced its safe and laws are altered to allow it to fully work to its designed potential.
As an example, I can take my hands off the steering wheel on the m/way and the car will steer itself, even around any bends, but its not allowed to self drive by law, so a warning will come up on the dash instructing me to put my hands back on the steering wheel.