This is because the Story Goal will be the common Concern shared by all the characters. When not seen as the Story Goal, however, Concern (in the Objective story) is descriptive of the broad category in which all of the objective characters' personal concerns can be found. For example, a Concern of Obtaining might have one character concerned with obtaining a diploma and another concerned with obtaining a raise at work. In each case, "obtaining" describes their concerns, but the specific illustration or "encoding" is unique to each.
In contrast, the Story Goal is the singly encoded concern SHARED by ALL of the objective characters. For example, all the character are concerned with obtaining a lost treasure. In this case, the specific treasure is of interest to every character in one way or another. It doesn't have to be the prinicpal concern of each character as an individual, but the one common concern shared by them all. Some may be for it and some against, but all share an interest in that singular concern which is, by definition, the Story Goal.
In stories, it is possible to have any one of the four throughlines' Concerns be the Story Goal. (The four throughlines are the four perspectives of a story from which an audience seeks meaning - Objective, Relationship, Main Character, Influence Character). Which throughline holds the story's overall Goal is simply a matter of the author determining which points of view he or she wants to emphasize - in essence, where the author wants the most commentary as the story unfolds. For example, if all the other characters are focused on the Main Character's Concern, that becomes the Goal of the story as a whole as well.
In most storys told in Western culture, the Objective throughline will be home to the Story Goal, simply because it is easier in our culture to visualize a shared goal from an outside perspective. Because of this convention, the Story Goal provided by the Dramatica software will ALWAYS be doubled up with the Objective Story Concern.
Since Dramatica, as a theory, is a completely new paradigm for story structure, when creating the software it didn't make sense to clutter the already daunting prospect of learning new concepts (such as the four throughlines) with too many alternatives - at least not at first. Once more people are familiar with the basics, future versions of the software will open up to allow the Story Goal to be selected from any of the four throughlines.