I'm just guessing here, but I'll bet there aren't any kids in this household. That glass enclosure would be one continuous smear of fingerprints and PBJ residue.
Or in my case, fingerprints and sweat as I grabbed for the invisible handrail. Bigger picture (and a couple of other designs) here. Warning: Picture on the right side might be somewhat (female nudes in a circle, shot from above like one of those old Busby Berkeley numbers) NSFW.