Optional Cabinets

Looking at the back of the two optional cabinets on my 3124kb, I noticed there was a latch at the top of the larger cabinet and the reciprocal part of the latch on the bottom of the smaller one. "Hmmmm....", said I. "This is curious. I wonder if they latch together?"

Sure enough, if you put the smaller one on top of the larger, the fronts lock into each other and the snap latch on the back holds them in place.

For the life of me I can't figure out the function of all this. There is no place large enough to mount them on the wall when they are stacked. Perhaps it is intended that they connect so they take less of a footprint on the floor during travel?

Anyone have any idea why you would want to latch these together? I have this lingering hunch that I'm missing something obvious