front and back being where most the lift is generated
You might find that the lift is constant all the way around. If you suddenly got more lift when the blades are fore/aft, the vertical vibration would be awful.
The retreating blade tries its hardest to create enough lift, battling the wind from behind.. The advancing blade has to throw away all that beautiful lift it gets from moving into the extra airflow. The only place where the fight is equal is fore/aft.