In the story, "Thank You, M'am" by Langston Hughes, the characters in the story speak in what has been called Black English. To me, Langston is simply using the sound of the language around him as a child, the sound of his people. The meaning of the phrase, "Maybe, you ain't been to your supper either, late as it be", is 'Maybe you haven't been home for your supper either considering how late it is'. Mrs. Jones is really commenting on the fact that she thinks Roger is hungry, hasn't been home to eat, and that is perhaps why he tried to steal her purse.
thanks for answering :) but i think she said that because she thought he's poor since he was out late !
He snatched her purse beacause he wanted a blue suede shoes not because he hasn't eaten yet !