Imposing arbitrary rules on my students in the courses I teach is one of the perplexing aspects of this job. Why set deadlines? Why give this or that penalty for missed deadlines? Why allow this and disallow that?
In general my approach is: the default is to have no rules, and rules can only be added if they serve some purpose related to the course. Broadly speaking, there are two purposes: one is to help the student learn, and the other one is to help the logistics so that the course runs smoothly. For example, requiring students to turn in homeworks at specified dates gives them an incentive to study with some regularity across the entire semester instead of cramming a few days of intensive study at the very end: it helps reinforce their self-discipline. Forbidding late homeworks after a certain point ensures that we have al the assignments turned in by the time we grade, preventing loose, isolated hand ins from floating around at random times and simplifying the graders' task.
The other day I was learning about Stanislas, a private prep school in Paris for students at the level and age of freshman and sophomore students in US colleges. I stumbled on some of their rules: no sneakers allowed. Student must wear leather shoes. No T-shirts allowed: students must wear shirts with collars. No long hair allowed for men: the students' ears must be uncovered. I was amazed. Where does that come from? How can that be justified? These rules seem completely arbitrary. Perhaps one might try to argue that students hear better if hair does not cover their ears, but what about the other rules? How does having or not having a shirt collar help study? I think that the person who created those rules had an opposite approach. Instead of starting from a default state in which there would be no rules, he or she started from some picture in their mind of an ideal student, and then created a set of rules to try to force the students to comply with their ideal image. The only limit was that rules had to be mild enough to be tolerated by the students.
What about our curriculum when we have one? Brown is very free in that respect, but other universities have mandatory requirements. Are those requirements arbitrary creations reflecting someone's ideal image of what students ought to know?