Why does Charley tell Willy to forget about Biff?

Willy is worried about Biff, and his plans to return to Texas. Charley sees Biff as an adult who can take care of himself.

Willy [after a pause, withering]: I can’t understand it. He’s going back to Texas again. What the hell is that?

Charley: Let him go.

Willy: I got nothin’ to give him, Charley, I’m clean, I’m clean.

Charley: He won’t starve. None of them starve. Forget about him.