Well if he had reanimated Rin and Tobi would have reacted shocked, we would have known that Tobi = Obito.
But at that time we were supposed to think that Tobi = Madara. That created the feeling that Tobi can't be Madara or that there is more between these two. That created suspense and kept us thinking about all that for 2 years.
Showing Rin would be too obvious. And besides, did Kabuto know that first Obito was Tobi and second that Obito saw how Kakashi killed Rin and third that Obito even knew Rin ? It's not that he read the Kakashi Gaiden Chapters and is perfectly informed on all the emotions between Rin and Obito.