You're forgetting that not all of the elevators go to all of the floors and the floors that they do go to are not always obviously marked. Couple that with the fact that some sets of elevators are called by a common control yet go to different sets of floors.

I believe that the monorails were taken into account when the terminals were first designed. At that time there were no security checkpoints. Things changed a LOT between then and the actual (lousy) implementation. Other airports have similarly ill-conceived entry/exits from their transportation systems. Look at the train at SFO. To get to/from it from where CO flies you have to go down the escalator, across the tunnel, up an elevator, over to the underside of the station, then up another escalator. It's much more of a mess if you have bags and need to use the ramps/elevators.