You know when you had lessons and your instructor was always yelling use your legs, shouldn't even need those reins.
Well if your reins were taken away could you honestly control your horse?
I went for a ride and the thought came to me, my answer is no. I dropped my reins and tried using my legs and my seat, he listens for some of it or not at all, but as soon as I touch the rein to go in the direction I want he goes that way.
So hypethically if you were riding your horse and the reins dissapeared somehow, could you still steer?