Batman's a terribly repressed individual. It all stern from his relationship with his mother, that deeply affected his psych. Deep down he's afraid of desiring and acting on his desires, because when he was but a boy and desired his mother, what happened? She was violated, in a way, by an act of violence. He got to see the pearls flying and her face in a state of ecstasy, of release, as she died, and he seeing all this probably came in his little boy pants at that moment in sycronization, but that transgression also ended up taking her alway from him. Forever. He felt abandoned by her. As if that happened because he had done a bad thing and was now being punished for it.
Now as a grown adult Batman can't stop himself from desiring things, from wanting a release, but he repress himself, out of guilt, out of shame, out of fear. He doesn't drink, he doesn't smoke, he doesn't even fuck. No partaking for this young man. He's perpetually in a state of want, of excitement, of arousal, of readiness. Always on the edgy. But he will never allow himself the release he so much craves. Because deep in his psych he feels that it is wrong to want and much more to get it. If he allow himself something terribly will happen and he will be punished for it.
Why do you think all his romantic relationships are with femme fatales? Because they're the forbidden, like his mommy was.