I take it you haven't driven a motorcycle. I can ride one, at speed and around corners, without touching the controls. Remember that the rider may represent 30+% of the vehicle mass. Moving your weight around on the bike has as much control over direction as the handlebars. Unless you are going to strap the rider into a seat (ie make it a car) attach him to a hydraulic arm, or install a 200lb gyro, no machine can take directional control.

This all comes to a head at the transition point of countersteering, where the controls reverse around 20ish mph. The rider's balance controls whether turning the handlebars right means right or left. If the rider isn't in sync with the autodrive, everyone is in the ditch.