Related question: What options are out there for 750s to go with a clear lens instead of the stocker?
The cut patterns lens, in combination with the bulb is what makes for a contolled beam pattern, particularly for the low beam.
The low beam on stock lights presents less light to oncoming vehicles and leaves a bit more on the shoulder of the road.
This can be seen best when directing headlights to a wall.
There might be clear lenses that do this as well but I havn't seen any...yet.