User blog comment:TheDarkKnightHasRisen/Best Pre-Nolan Batman Film?/@comment-5019018-20120817190205/@comment-5557876-20120817191941

Well, he left because the city didn't need him anymore. When The Penguin appeared, the city shined the Batsignal, or whatever, and he came back to help the city. At least that's what I think.