What is real reason Dill ran away from home?

Dill felt left out and unwanted. No one paid any attention to him.

“That wasn’t it, he—they just wasn’t interested in me.”
This was the weirdest reason for flight I had ever heard. “How come?”
“Well, they stayed gone all the time, and when they were home, even, they’d get off in a room by themselves.”
“What’d they do in there?”
“Nothin‘, just sittin’ and readin‘—but they didn’t want me with ’em.”