Actually, if the goal is to gauge students' progress and make grading easy, you can get that same effect with periodic short quizzes and occasional exams. There are loads of college classes that do this, and make homework assignments optional. Loading students down with vast busywork isn't necessary for tracking and easy grading.

I think the main reason why students get lots of busywork is because it feels like diligent teaching, and it's relatively easy. Cynical of me, I suppose.