5. He's Allergic To Retirement
At the end of The Dark Knight, Batman is the picture of health: he is pretty much in peak condition, both physically and mentally, and his decision to retire to preserve Dent's reputation is designed to be a monumental waste of resources. But in the eight years between the end of that movie, and the start of Rises, something very odd happens that brings Bruce Wayne's status as a bad-ass firmly into question. While Bruce Wayne is holed up in his mansion like some grumpy-voiced Miss Havisham, he somehow falls to pieces. He stops training yes, but removing his body from direct physical threats seems to make his bones, ligaments and tissues crumble: by the time he is diagnosed by his off-puttingly familiar doctor, he has somehow degenerated into an old, broken man. Clearly, this is symbolic: but some form of wasting would have worked just as well as suggesting that inactivity can somehow HARM Bruce Wayne's body, and make all of his old injuries come back. Yes, conditioning comes into it, but debilitating injuries are not fixed using intensive training and combat - that's just not how it works.