When students write at least two papers, they learn from the first one and generally do a much better job on the second. Assignments are given out in written form. We could cite countless Writing Center consultations in which students have come to us for help with a draft, but they have nothing in writing that states what kind of paper they are expected to produce. Consequently we have not been able to give them the help they need. Means are provided for students to write drafts, get feedback, and revise.
Revision is one of the most essential parts of the writing process.
So a lot of papers come in as first drafts. When this happens, students don't get much benefit out of doing the assignment. Also, the instructor suffers a lot more agony trying to deal with the papers. Feedback can come in many forms. Students might bring drafts to peer-response sessions and critique each other's work.