In my opinion Donald Ross used the fore bunkering to orient the player to the preferred line of play. While this may not be the case in every instance, I believe it was his intention most of the time.
Visualize the hole with out the trees, little or no definition between the fairway and primary rough and you can clearly see the need for these bunkers. Especially when playing over slight rises which obstruct the view .
I love em and would restore them all if I could.