Itachi didn't move. He was far too exhausted for that. But he did answer.

"Because... I honestly expected to die, for you to kill me... It wouldn't have mattered. Coming here... changed a great deal of that. And the other eye... One day... I feared you might need it too." He whispered. "This just... wasn't how I ever wanted to imagine it."

Self interest? Itachi doesn't know the meaning of that word, especially where Sasuke is concerned.