I can't speak to using CAD, as I've never learned anything about it. That said, gear planning and making can be enhanced by good drawings. Some sort of measurable planning can prevent costly mistakes. I've seen people make scale drawings to see if pieces would fit together for tents, for example. Computer files are easy to share and send, as well, with the added advantage of often being more legible to a larger audience. One specific example would be a hand-drawn sketch sketch compared to a PowerPoint drawing of a hammock.