The reason I think is because it really boils down to common sense.
Even though it might get in the way of playing outside or watching your favorite television show, it's necessary and, believe it or not, good for you! Parents rarely get to spend much time with you while you're at school.
Homework allows them to keep up with what you're doing in your classes on a daily basis.
Lessons learned along the way are, time management, responsibility, discipline, and study habits.
The positive thing about learning these skills is that in the higher grades of school the parents and teachers input become less and less. The act of becoming an adult means making more and more decisions on your own.
This paper will explain the educational benefits of homework through the view of an expert.
The information you are about to read is from a professor of Duke University.
For example, before beginning a discussion of a complex period in history, it can be very helpful to read background information as homework the night before.
Homework also gives you valuable practice with what you've learned in the classroom.
Without homework, a lot of classroom time would be wasted with repetition that could more easily be done outside the classroom.
In these ways, homework expands upon what is done during the day in the classroom.