This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Because in that example the request is being made from an HTML page, outside of the Struts 2 application. Without the extension (by default, anyway) the container wouldn't know it was a Struts 2 action request.