Yes, visual diagrams and shapes are sometimes more efficient. But the main point is that text is the lowest (and cheapest) form of encoding that is still human

Yes, visual diagrams and shapes are sometimes more efficient. But the main point is that text is the lowest (and cheapest) form of encoding that is still human readable/writeable. Text is always there even when other data formats are not feasible. If you can adequately represent your ideas in text, you are giving it the highest chance of being seen and distributed by other humans. You don't need special tools or artistic skills to replicate the data, anyone with a pen & paper or keyboard can do it!