Or, maybe he wants Casey to stay on the run?
If Cindy (we can only hope) had any concern for her mothers peace and quite during her dying days why would she test the waters? Maybe bringing Casey home while Shirley is dying could be her idea of people feeling sorry for her and letting her get back to where she said she wanted from jail. I remember her "I just want to be home with my family" statement she made from jail. That's all she wanted. Not anything for Caylee at all.
You know if she's confessed to an accident, even after thirty one days, she'd be on with her life and we'd never heard anything more about her. She would be just another mother that screwed and was scared. She'd wouldn't of had any jail time and she'd be on with her life.