Design takes many forms. From sketching through clickable prototypes, Rob uses the tool to fit the need. And that need is to communicate design to key stakeholders. Rob uses sketching for design exploration, then creates wireframes once the number of alternatives are reduced to the best ones for the project. As an interaction designer, it is also important to demonstrate behaviors, so he will sometimes provide interactivity to explain a concept to stakeholders.
If a developer simply translated requirements into a working product, it may not be fun or easy to use. Experience designers come armed with research to fuel many design iterations, with the goal that they can design a product that is easy and fun to use.
Rob has created designs that have reduced clicks and page loads. He also has straddled the line between adding more functionality and stripping away functionality to make things simpler to use.