The main reason I like to use rubrics is so I know I am treating all students the same. If points are assigned based on specific criteria, then I do not have to worry that I am treating one student's work different from another. It also gives me the opportunity to give consistent feedback to students so they are all hearing the same things from me. After teaching the same subject so many times, you forget whether you mentioned certain things to everyone or not. And if so, did you describe them the same. I save my comments and refine them every time I teach the same course, but I know I am providing the same quality feedback to everyone.