This article talks about either the absent parent, or the ineffectual parent, or the dead parent, etc. Any of these set up the protagonist of the story to need to solve his or her own problems. I've thought about this charateristic of YA Lit quite a bit. But it doesn't always happen that way. Chris Crutcher, though he doles out his share of bad, abusive, and ineffectual parents, also has kind and helpful, honest, good adults or parents available in some of his young characters' lives. I think that's one reason I like his stories: there's a realistic balance, and besides the fact that kids can grow and learn to solve their own problems, there's the fact that helpful adults exist and are avavailable to help through tough times.
Anyway, the article is worth reading: