It depends on so many factors. There is no “one answer that fits all”. To the parents who say that their daughter has to get good marks: Maybe they are using this as a tool for their bright, capable daughter who is not really motivated to study.
To the parents who are willing to pay? So what? Maybe the girl had a hard year? Maybe she had a tough nisayon and the parents want and need to give her that. Maybe none of the above. One thing has nothing to do with the other. I just want to mention that children who earn their money, have a much greater appreciation for it. I am glad you are not jealous.