Because he has problems letting go. You know how most people, the death of their parents remains with them the rest of their life but they move on? Not Bruce.

I know he still gives a shit. But he made a choice. Me, or the psycho murderer who killed me and killed hundreds of others and put Barbara in a fucking wheelchair, and he chose the clown. I'm pretty sure we're over.

[The choice of words was deliberate and the tone is ugly, bitterly self-mocking, borderline self-loathing.]