Atticus probably felt that Mrs. Dubose's highly private medical dilemma was none of his children's business. He also may have felt that they were too young to understand. It is possible that no one else in Maycomb--aside from the doctor and her housekeeper, Jessie--knew about Mrs. Dubose's morphine addiction or her desire to kick it. From a professional point of view, Atticus was probably legally bound to keep such a matter private. He explained to Jem that she had summoned him to make final preparations for her will, so he was also being paid (unless he performed his tax for free), and all such matters would have been of a private nature.