The Nintendo 10

[VGPolyglot]

If the Game Boy, Game Boy Color and Game Boy Advance are all counted as one, why are the DS/3DS and Wii/Wii U considered separate? Also, what about the Game & Watch or the Color TV game? Not forgetting the Pokémon Mini or Virtual Boy, as well as the Famicom DIsk System and Nintendo 64DD add-ons.