[Image source: this article]
Hand-drawing diagrams on a white-board and on paper is an important practical skill (e.g., for technical interviews, project discussions). It's possible that the diagrams you draw in your first few attempts to look amateurish, messy, and hard to read, and the drawing itself will take a long time. With more practice, you will be able to draw such diagrams quicker (e.g., draw as you explain verbally your design), with less need for corrections, and the diagrams will look more professional too.That is why we have structured these tutorials to get everyone to practice this skill so that your first few (not-so-good) diagram drawing experiences happen in the tutorial, not in an interview or during your internship.
Note the following: