Why does Maniac Magee leaves home?

Maniac Magee left his home because he couldn't stand his aunt and uncle's selfishness any longer. They were described as having two of everything--one for each of them--and they wanted to split Maniac up between them.

Later on in the novel, he leaves the Beales because he feels guilty for causing them trouble (the town is very racist, and several townsfolk were terrorizing the Beales for taking Magee in).