you can rest your hand on the steering wheel without affecting direction, so fatigue goes down on long drives (can't be said about a joystick). Very repeatable variable control. You can even use with your knee while eating fries. (try and do that with a button or joystick) They are also large enough to allow manual steering if/when power steering goes out, by loss of a belt....so you can still steer to the side of the road without dying. You can also get very sharp turns by full rotation of the wheel, and even turn with the palm of your hand.

Plus most everyone has been trained on how to use them.

I think that the steering wheel has been reinvented many times over as time has gone on, and will continue to evolve.