Users are human and humans are goal-directed systems.
Easy to say, but definitions of users and goals are hard to find in software design methodologies. Even rarer are user's individual goals captured by the software itself . Interaction designers now and then talk about user goals, but the relationship of that talk to the designed interface is wispy. Maybe designers get some of their own goals into the software, but they don't build software that learns anything about the goals of the individual user. When goals are delineated, the simple act of clicking on a link or closing an email window can efficiently convey multiple levels of user intention to the software.