
Continuity mistake: During the interrogation scene, when Batman beats up Joker, Joker's hands are holding Batman's forearms upside down (from underneath). When the frame changes his hands are now on top of Batman's forearms, then it cuts back and his hands are under again. (01:28:00 - 01:29:00)
Answer: It's habit, and a sensible one at that. When he's in the mask, when he's being Batman, he uses the voice, even if the person he's with knows who he is. If he drops back to his normal voice with some people, it sets the precedent for using it while wearing the cowl, which means that he's more likely to slip up and use it around people who don't know, potentially revealing his true identity. If he sticks rigidly to using the voice when kitted up as Batman, regardless of situation, it minimises that possibility.
Tailkinker ★