Teacher? The Rat Ate My Homework
While most people assume that notebook margins are there for teachers to leave comments, that’s a common misconception. In reality, margins started being added to the paper in order to protect people’s work.
Earlier in history, having the edges of your paper chewed off by rats or insects was relatively common, so people who wrote all the way to edge would lose work. By establishing large margins, it gave the rats room to eat away with a lesser chance of them ruining a piece of paper with writing on it.