Madara used Kakashi's eye to get into Obito's dimension. But if he plans on replacing that eye with his rinnegan, how is he gonna get back out? Unless he can use kamui with that rinnegan, which I doubt.
But he couldn't find his corpse, which he needs.
Edit: Kushina also died after Kurama was extracted from her. Is she were to be resurected, she won't have Kurama.
I think Kabuto specifically stated that he was unable to get Jiraiya's DNA. In So6P's case, it'd ruin the manga, imo, even if he was somehow able to get his DNA.
I think it's mainly because of how she still has a mad, unhealthy obsession for a traitor that never cared for her, and even tried to kill her. Same goes for Karin, and Ino. The war showed that even Ino was still obsessed with Sasuke.