Obito didn't have a jinchuuriki for him, plus if he revived him with the Six Paths technique then they would have had to get rid of one of the tailed beasts that we hadn't seen much of yet. But I agree he should be more involved somehow
Kishi needed the 6 Jinchuriki to have some screen time so we can see their abilities and stuff, we have already seen the Shukaku in action in Part I but I agree we should have seen him at least one more time.