Ever notice how many main characters are shy? How many find solace in reading? How many want to be writers?
Writers aren't all the same, obviously, but many of us have certain qualities, particularly that last one. And it seems many of us tend to stick our own traits into stories, either deliberately or by default. As a young reader, I enjoyed being able to relate to so many characters; a lot of my own favorites have these quasi-Mary Sue tendencies. But somewhere around fifth or sixth grade, I picked up a now-forgotten book whose main character mentions that she'd rather watch TV than read, and I thought, "Wait, that's wrong... but why should it be wrong?" Suddenly, it seemed unfair that only frequent readers got to see themselves in books.
I think the canon as a whole has gotten better at depicting kids who have other interests, but it's still something we as writers need to keep in mind. Of course we should show some shy kids, and it's hard to resist giving one's main character a favorite book. But if I were a kid who felt iffy about reading, and all the main characters I encountered insisted that reading and writing were the Best Things Ever, I imagine I'd feel that I didn't belong in this book world.
I have no interest in keeping this club exclusive, and I doubt anyone else does, either.