Elevator Defaults

I am genuinely curious about the behaviour of the elevators in the building where I work.  As I am frequently in on the weekends, and often the only person in the structure at that time, I have noticed a peculiar phenomenon that others probably miss.

Some background:  the building has seven floors, plus a basement.  There are two elevators – the one on the left serves the main (ground) floor through 7; the one on the right goes to the basement as well.

When either elevator drops you off, it doesn’t stay where it left you.  The one on the left always goes to rest at the 4th floor; and the one one the right always goes to park at the fifth.  ALWAYS.

It would seem to be a waste of energy to move the cars for no reason, especially since if it has just discharged a load on the ground floor, that’s the highest probability for the next rider to summon it to.  Why not just stay there?

I considered the fact that they may go to some mid-point where they can respond most quickly to a request from ANY floor, but that doesn’t make sense – if they were trying for rapid response, the one on the left (which services 7 floors only) should indeed hang out at 3½ (so we’ll say 4 is OK), but the one on the right (which also handles the basement should be at 3, not 5.  AND, when I am calling a car to the ground floor from their default resting places, the one from 5 always comes to get me, not the closer one.

Is it possible that it takes more energy to hold a car at G than at 4 or 5?  Is that why they always return to those floors?  Does anyone know anything about elevator efficiency algorithms? 

As an aside, I wonder about the naming conventions of “floors” and “stories.”  In Europe, the main (ground) floor is usually called “Main” or “Ground” or “Lobby” or something like that.  And the level directly above that is called “1.”  In North America, the floor immediately above the ground level is called “2.”  Do you think it’s because when the first two-story structures were built, the upper level was the only one with a “floor,” since the main level would have dirt or mats or thrushes or something other than a floor?  So the second STORY had the first FLOOR.