Which I never understood. Ron and Hermione is serious bad writing. JK grew as author as the books went along, but that part was always seriously weak, especially in comparison to what she had going on with Harry and Hermione. Like her losing it because the Department of Mysteries. In an effort to make Ron and Hermione work, and it never did, she messed with the Harry/Hermione relationship (I call it randomly grouchy Harry), while forcing Ginny into the situation. It is why HBP isn't near the other books, as a lot of it is a game of trying to make the wrong work.