Because it addresses SO MANY THINGS and attempts to explore them:
- Gender roles (in which this book series destroys them)- In this series you have a HUGE burly man (Hagrid) who treats animals like they are his children, cries publicly, shows his emotions, KNITS IN PUBLIC, and gardens. You have Mrs. Weasley who is the major mother-figure for Harry but who fights just as hard in the final book as the men even though she’s “just” a housewife. She kills Bellatrix for crying out loud!
- Racism and privilege– The full-blood, half-blood, muggle-born aspect runs throughout the whole series and is meant to be seen as a type of racism. Hermione is a muggle-born but her abilities far surpass her peers’ and Neville, who is a full-blooded wizard is expected to be a better wizard simply from his ancestors, is one of the worst in his classes.
- Classism- The Malfoys vs. the Weasleys.
- Ageism– Harry isn’t taken seriously because of his age (in fact it actually helps him obtain the fake locket with Dumbledore because he isn’t seen as a “real” wizard due to his age) and neither is Dumbledore. Dumbledore’s age becomes an issue for the news and people start to question whether or not he’s gone senile when he and Harry claim that Voldemort has returned.
- Speciesism– The treatment of House-elves, centaurs, giants, and other magical populations are seen as beneath wizards and Hermione tries to take steps to fix that with S.P.E.W.
- Education– Hagrid was expelled and so he’s seen as uneducated and Malfoy calls him a servant, a savage, etc. But he’s able to earn a position as a teacher at Hogwarts and overcome his lack of an education. Fred and George are the same way, they drop out of Hogwarts and become successful joke shop owners, the implication being that they were not ever really suited for a traditional education (they were not traditional learners and that’s okay). Or when Harry becomes the DADA teacher during Order of the Phoenix, he chooses to teach it hands-on while Umbridge has them write lines all class period. This book explores different learning styles and shows that there are many different ways to learn a subject.
- Ableism– Neville’s parents live in a hospital because they experienced severe brain damage after being tortured by Voldemort for information. We see them in Order of the Phoenix and it’s through those chapters that we not only understand Neville better but we find out that he isn’t ashamed of them nor does he feel he should be.
- Sexuality- This book portrays a gay relationship, (even though it is not brought up within the canon ever): Grindelwald and Dumbledore. JK Rowling stated this shortly after the final book came out, that’s how we know this.