Yea it's been discussed before but it was such a weird addition to the manga I'm not surprised people are still baffled by it. I did a thread on it one time too and got a few people to try and come up with a sensible explanation but ended up making them agree with me in the end. In no way does it make sense. Some of the responses I got that got shut down:
"They were stealing each other's eyes in order to reuse Izanagi" -- This made no sense because the manga didn't say that they were fighting among one another, but they were bickering over the best outcome for a mutual battle. Basically, they were fighting over the best way to reach the same goal. Stupid
"Izanagi doesn't just go away after the first use, you can deactivate it if you want" -- Obito, who had senju dna, which we know increases the length of Izanagi, could only use it for about 5-10 minutes against Konan before his eye went blind. And that's a uchiha WITH senju dna. So imagine how fast the other uchiha's eyes went blind.
"Izanami makes sense because it kept Uchiha from losing their eyes" -- So basically, A uchiha would use Izanami and lose his eye just to keep another Uchiha from wasting theirs. Again, makes no sense.
Personally I didn't like the Izanami introduction. It honestly makes the Uchihas look retarded imo. There's just no way to justify the stupidity of it
