When you fade the ball, the force going through the clubface and the perpendicular line from the clubface become further apart creating a more 'glancing' blow meaning less energy is transfered to the ball, meaning that the more your shot goes shorter increasing the degrees off-line. The effect as the clubface being slightly open will send the ball higher initially until the 'openness' is enough to decrease in energy transfered to bring the ball flight down again decreasing the distance and increasing the degrees off line for a reasonably executed procedure. As the line of force and the line perpendicular to the clubface become further apart will increase height (initially as mentioned previously) and spin, the ball will stop far quicker than a draw which again increases the margin of error in terms of degrees off line.
The idea is to hit a shot that if any curvature is going to occur that it will err on the side of the fade to increase your margin for error hence fade bias...
Assuming sufficient ability, this is the prefered stroke 'from a technical standpoint' on a standard straight fairway.