The conversation between human and AI assistant.
Why were the Dursleys allowed to treat Harry the way they did? Why did the neighbours or teachers not report them to the appropriate authorities?
That's true. But why do you think the neighbours or teachers didn't do anything? Surely they would have noticed something was wrong.
It's possible that the Dursleys were very careful to keep their mistreatment of Harry hidden from the outside world. They may have even lied to Harry's teachers and neighbours to cover up their behavior.