Creating 2D drawings is an art – knowing what information is required and how to display it in a readable arrangement, while being efficient with the space provided, takes certain skill and experience. It used to also take a steady hand when a piece of paper and a pencil were the tools of choice. When CAD systems found their way into industry, capturing information in an electronic format was both a faster way to get the job done and provided a more consistent presentation of information.
A 2D drawing is ultimately intended for human interpretation. A human will look at the drawing and read its information in order to manufacture and/or inspect the part (either manually or by programming a machine to do it), so the human capturing the information in the drawing has to be thoughtful about doing so, ensuring the information that the manufacturer, inspector, or assembler needs will be shown on the drawing.
The “problem” with the art of capturing such information in a drawing is that information may be easily misinterpreted or lost.