It's not just about turning the wheel, though, is it? I would assume that much like when driving a car, it's a longer process of being a human PID controller and making small adjustments to angular acceleration based on feedback from the system. It might be useful to remove this mental load from the decision-maker.

When my family drives places we have not been before, the driver focuses on the road and the passenger seat is navigating, planning stops, etc. Sure, the driver could read them off of a GPS unit and improvise stops, but it is safer and (in our experience) better to have a separate person focusing on thinking and planning.

But also it provides a secondary check on the sensibility of the order. If my wife says "take the first right in this roundabout" and the first right does not seem like the way to go, I will do another lap and ask her to double-check. I can do that because I've been surveying the alternatives well ahead of time, which I could do only because I was not focusing on navigating.