Why do they do it?

I'd love to know why it is that parents insist on doing their childrens' schoolwork. Do they get some feeling of accomplishment out of doing a 6th grade assignment? Please, enlighten me. I have been engaged in battle lately with a parent whose child refuses to complete any assigned work. Consequently, he has a failing average. In the past week, I've been promised the missing work to be done in in-school suspension, done at home, faxed in, dropped off. So far, not one single piece of paper. It's obvious to me that the child is manipulating the mother into doing the work. The problem with that scenario is, simply, that she was not present for the lessons or instructions, and therefore has no idea what needs to be done. Of course, the child couldn't possibly give an accurate account of what work is pending. Did I mention this student is 14 years old and due to start high school in the fall?