Just as having a top-loading fridge is useful because you can pack more into it, so too is it useful to have top-loading shelves below the bed surface.
The higher you make your bed, the more storage space you can have under it. There's a limit to the height, because at a minimum you have to be able to sleep on top of the bed (and I'm fat). Also, it's useful for the bed to serve as seating space when you have guests over, however I might sacrifice that in favor of more storage space.