With each new iteration of digital tool packages, the goal (and the marketing claim) is that it mimics analogue mark-making better and faster than the previous version. While I am not here to argue that an older way of mark-making is better than a new one, I believe that digital and manual ways of image making can inform each other. Further, the current batch of college students have grown up without knowing life without the existence of digital manipulation tools. I see them typing on their phones with a velocity that seems impossible to me. And yet, when asked to draw some simple shapes with a pencil, they seem to lack the same skill and courage of my little nieces and nephew.
Thinking specifically about art classes, students need to build skill-of-hand. They need to learn how to manipulate a surface with a mark-making tool. Drawing in the margins, without a goal in mind, can start developing the required manual dexterity needed for success in many art-making endeavors. For experienced artists, it can serve to keep the drawing muscles loose. It can also serve as a source for new ideas. I tend to stick to formal elements. I have colleagues, who are more content driven, who draw little stick figures while talking on the phone. These drawings might not be finished. These drawings might not be very serious. But, these drawings are marginally important.