When you are negotiating a corner, you have a three variable system with two degrees of freedom. Out of lean angle, turn radius, and speed, you can choose two. The third variable will be dictated by your other two choices and the constraints of the physics of the system. If you pick a radius and a speed and don't lean in far enough, you *will* fall over toward the outside of the turn. If you lean too far for the radius and speed, you *will* fall toward the inside of the corner.

Turning your bars more or less is just a way of choosing the radius.