1. Students will frequently just try things until it works, move code around, etc., leading to very messy code. 2. Graders often do not look at individual assignments unless there is a reason to do so, often relying on automated test suites. And when they do look, I'd bet their first reaction is something like "I don't know why they're repeating themselves like this, but my rubric only penalizes them for 5 points here..."