Some angles and conditions do call for this on the lens, when you can't really use your hand, especially if operating remote. It's well made from metal and can offer some protection to the lens from attack, but ideally use a clear/uv filter, as well, when working with hostile subjects. Nikon should incorporate this into the lens as a slide out hood, just like they've done on other lenses like the 80-200mm f2.8.
The lens it goes on, the 200mm f4 micro, is an exceptionally good lens and if you can get one do so while they're still available.