Why did bud try to fall asleep before Momma was done reading the story at night?

Bud tried to fall asleep before Momma finished reading the story because he wanted to avoid the discomfort of facing her emotions and the reality of their situation. By pretending to be asleep, he could escape the tension and sadness that often accompanied their bedtime routine, allowing him to maintain a sense of security and distance from the pain of their lives. This act also reflected his desire to protect himself from the vulnerability that comes with being emotionally close to others.