Why were the Pickwells impressed with Maniac in Jerry Spinelli's Maniac Magee?

The Pickwell kids were impressed that Maniac was running on the steel rail of the train tracks. 

Maniac goes to the Pickwell house for dinner because the Pickwells have a lot of kids, and when Mrs. Pickwell called them to dinner, Maniac came too.  During dinner, no one mentioned him.  After dinner, Mrs. Pickwell asks her kids who he was, and all of her kids thought that he had been invited by someone else.  

By the time they went to question him, Maniac was gone.  They saw him running down the railroad tracks with his book in his hand.  The manner in which he was running was very impressive. 

He was running, passing the spear field now, and the Pickwell kids had to blink and squint and shade their eyes to make sure they were seeing right -- because the kid wasn't running the cinders alongside the tracks, or the wooden ties. No, he was running - running -- where the Pickwells themselves, where every other kid, had only ever walked -- on the steel rail itself! (Ch. 6) 

This is another example of Maniac making a reputation without meaning to.  Maniac’s legend grows because he has a tendency to do extraordinary things either because he does not know about the local prejudices or because he doesn’t care.  Maniac just acts according to instinct, and everyone thinks he is amazing. 

Later, Maniac returns to answer the dinner call again.  The Pickwell kids treat him like a hero. 

This time, of course, there was a difference. He was no stranger. He was Maniac Magee, the kid who had walked barefoot through the dump near their house. The Pickwell kids cheered when he showed up and treated him like a legend in the flesh. (Ch. 40) 

Mrs. Pickwell treats Maniac like a member of the family.  She likes to take in strays for dinner.  She is just a genuinely good person.  However, being with the Pickwells makes Maniac miss the Beales, who he feels are his real family.