Because the wizard loathed Hermione and she was supposed to dislike him. But after working with his arrogant ass, she found she rather did not mind him. He was perhaps a bit gruff, perhaps even borderline rude, but he was brilliant. She was not sure if it had been puberty or the war, but he was far more quiet than she had imagined him to be as well. Lost in his own mind, he seemed to be more an observer of the world around him than one that actively engaged until he had to. 