As a student myself, I found that many of my peers, over time, lost the want to learn, and with it, the motivation to do the homework. Children do not become educated by simply being forced into doing assignments—they must have that curiosity brought up in them from the start, and with it will come a better turnout rate in homework.
At the same time, much of the cause for that loss is the fact most of those assignments are simply busywork, given as a result of good intentions but still busywork. Much of the actual learning process should be going on in the classroom.