There's really no need for more than one hand on the wheel unless you're turning, in which case you shouldn't be using radio controls anyway.
Consider that at a critical moment the difference between moving a thumb and moving ones whole arm and hand could be the difference between life and death.
EDIT: fixed typos
For everyone else, we've had automatic cars for forever. There's also a video online of a man with no arms who learned how to drive their car without them.
Edit: changed to be specific about the one hand on the wheel.