I think what the OP means is why doesn't Obito use a spare Sharingan and insert it into his eye socket
and cast Izanagi.. maybe it takes a medical ninja to perform the transplant... , but Obito didn't have any medical ninja around him when he used it *IZANAGI* against Konan. He already had the Spare sharingan Inserted...
Who did the insertion is the question??? Was it Zetsu??? *they are pretty smart* or was it Obito himself???
Or did he perform genjutsu on a regular medic and force her to do it, then maybe kill her to hide his whereabouts...
Did Obito even have a spare sharingan in the War??? By all means he most likely should have.. I mean this IS WAR..
he used one against ONE Kunoichi, so why not have spare sharingan against an army of united villages.
Was Obito going to die after the wound by Kakashi?? Probably ??? & maybe Obito left Kamui dimension
to insert another sharingan and then use IZANAGI to undo his wound.....
I think AFTER you use IZANAGI the sharingan loses its light around a minute or two later... and closes.. but not instantly..
But being smart or at least reasonable, it only makes sense for Obito to have a spare sharingan..
Afterall he did have a lab full of them...
The only sharingan Obito had was his Kamui one, he'd rather have Kamui than Izanagi since there's only 1 Kamui ..
(not Kakashi's )
I wonder if you could use IZANAGI multiple times with the SAME eye before the curse takes effect and it closes FOREVER.
also if Obito would have tried to insert a spare then, he would have to remove one of his eyes, most likely the Rinnegan, then Kakashi would take that opportunity to land a finishing blow again.