Engineering deals with ideas and the implementation of ideas, and an idea is of limited use if you can't communicate it. An expensive idea will never be developed if you can't convince someone to fund it. An idea developed into a product will not be successful if you can't convince anyone to buy it. Your product can't be sold in large quantities if you can't describe how to build it to the people who will manufacture it. Unless your product is completely intuitive to use and absolutely reliable, people will stop buying it if you can't explain how to use, maintain, and repair it. Finally, if your idea is a good one, other people will steal it if you don't patent it, and you can't patent it if you can't explain how it works. The gist of this is that without adequate documentation a design is not useful, or more succinctly:

During the course of your project you will produce a number of documents and give a number of presentations describing your design, the reasoning and analysis behind it, and its ultimate realization. Each of these will have a particular purpose and be directed toward a particular target audience, which will shape its content, format, and style. The following sections provide a brief summary of the basic requirements for each of these documents and presentations.

Presentations