Why did bud's mother never tell him about his grandfather?

When Bud is six years old, his mother passes away at the age of twenty-six, and he is taken to an orphanage. He eventually leaves in hopes of finding his father. Although Christopher Paul Curtis does not explicitly tell the reader the cause of Angela's death, he does give insight into how she died. In chapter 11, Lefty Lewis's grandchildren, Scott and Kim, ask Bud about his mother. Bud tells them that his mother got sick and died a short time after becoming ill. Bud also mentions that his mother's death was quick and peaceful. He tells Scott and Kim,

My momma died so quick and painless that she didn't even have time to close her eyes, she didn't even have time to make a face like she was hurting (Curtis, 77).

In a conversation with Herman Calloway in chapter 19, Bud explains to his grandfather how Angela died. Bud tells Herman that his mother did not go to work for six days in a row because she was feeling ill. When Bud walked into her room one morning, she was dead. He also mentions to Herman that Angela died in peace and did not seem to experience any pain.