Simple, because they did not have the beasts within them. The beasts were already inside the gedo mazo. It just happens that they keep the powers and chakra they died with. It was still the beasts chakra so they could speak with them etc but it is not the originals.
The same thing happened with Madara in his death. His eyes were given to Nagato upon his death. Obito took the eyes back and put them into himself as we can now see with his left eye. At the same time, Madara is resurrected with his eyes while Obito is still in possession of one.
We see is again when Itahi was brought back. Sauske already had his eyes and yet Itachi is revived with his eyes intact.
That is why they have their jinchuriki abilities. The beasts are not able to be sealed within a dead body but the beasts were no sealed within them while dead. They are merely empty vessels with the replication of abilities.