Dick did try to leave Batman behind. Gotham wouldn't allow it. It had to fall on somebody, and he wouldn't let it fall on his brothers.

"Closer to twenty," Dick admits after a moment of doing the math. And breathing through a moment of old grief. "But you're right. He's such a big part of our lives and none of us were ready when we lost him. We're lucky." Again. They always manage to get lucky about this. "Even now, I play a lot of 'what would Bruce do' when I'm considering an action."