Maybe I'm wrong, but I notice that Nikon's newer lenses don't have an aperture ring. For example, an older AF 35 mm f/2D is now replaced by AF-S DX 35 mm f/1.8G, or AF 50 mm f/1.8D is replaced by a newer AF-S 50 mm f/1.4G.
I never used a D-type lens, but I believe that it is much easier to rotate the aperture ring on the lens than pressing a specific button then rotating the wheel on the DSLR body when you need to adjust the aperture (and it always annoyed me to do it this way, since I often change aperture and I can't do it while keeping the camera at my face with a finger on a shutter button).
So why is the aperture ring removed more and more from the Nikon lenses?