After five minors, a student will face some form of minor consequence. It's like in larger society: when there is a deluge of some type of antisocial behavior, if it is not stemmed immediately, it becomes tacitly accepted and more and more common. Think of the Broken Window Theory of criminal justice. The principal's daughter, an honor roll student, was busted last year in math, for crying out loud. The students know that they are likely to get away with it, so the certainty of punishment variable is largely gone, and then to compound it, the harshness of punishment is minimal. Anyone can do that math.
The central reason I'm hesitant to go to paper-only, and all writing in class is a practical one: the handwriting of students is unreadable. More than half the time, they can't even make out what they wrote.