Harry Potter explained: "Dumbledore much prefers being able to organise things so that someone—Hermione, say—is gifted something she can never get otherwise, and it’s handed to her by the outstretched hand of Albus Dumbledore. He prefers this because One, this would make Hermione say, "Albus Dumbledore is so kind and generous’—and public adoration, Dumbledore eats it up with a spoon. And because Two, if Dumbledore can organise Hermione getting some great position that she can never get without him, he will own her. He can demand favours from her for decades—look at Remus Lupin. The last thing Dumbledore wants is someone like Hermione being hired for a position because she has better test scores then most Purebloods, so the law says to hire her, and Dumbledore getting no credit for her being hired."