It was built (originally at Disneyland) as an elevator to LOWER guests to the floor below the entrance level
so that guests could walk UNDER the railroad tracks and "outside" the berm (raised hill area) into the HM show building, which was built "outside" the DL regular area (in part of the DL parking lot.)
When they built the MK version, they duplicated the then famous stretching room for Florida guests. (The MK version does not lower guests at all, it is just an "effect.")