They like the familiarity of Molly Weasley;s antics.
Possibly. But they also like consistancey and for things to make a certain amount of sense. When the first book came out, Shannara was in the targeted age bracket and she wanted to know what was up with that. Years later when I finally got Josh to read them, he and Shannara were talking about it later and even he thought it "Smelled like a set-up." Of course, he may watch too much James Bond.
Harry's childhood and home life are meant to be evocative rather than rational.
It's scary, is what it is. Harry is an abused child. What we see in the first book is bad enough. How they continue to treat him as the series progresses is horrid and frightening for the children these books were supposed to be aimed towards. The books would not have been offered on the shelves of La Petite.