I think you've misunderstood - while there are many models with the ability to steer the car without human input, there are almost none that do not have a direct mechanical link in addition to those systems so that the human can override those controls in the event of malfunction.

For example, this is the steering colum from a Kia Sportage with lane assist:

You can see that while it does have supplemental electrical controls, there's still a purely mechanical connection. I will admit I made an error in my initial post: Teslas do not use steer-by-wire either. As near as I can find there are only four models (in the US) that do not have at least a supplemental direct mechanical connection - and current safety standards make it borderline impossible for new models without that to be legal on US roads.