Board Thread:Naruto Discussions/@comment-26488946-20150612205152/@comment-4912646-20150613015938

Even Madara himself didn't use any Sharingan abilities while his Rinnegan were active. Instead he (or his wood clone, to be precise) purposely deactivated his Rinnegan when we wanted to cast genjutsu. It seems the only ability shared by the Sharingan and Rinnegan is seeing chakra, which is something all known dōjutsu are capable of. As for why the highest form of the Sharingan seemingly cannot use its most basic "Dōsatsugan" and "Saimingan" abilities, that's anybody's guess.