I have to wonder if it turned out to be more the case that the actors who played Harry and Hermione went through a fairly uneventful transition from child to young adult. The kid who played Ron, on the other hand, went through the gawky and somewhat unattractive goofy teenage phase (like most normal humans
)
Ron was actually my favorite character in the first movie. I was disappointed that Rowling & Hollywood turned him into such a whiner as he got older.