Why would anyone want to make stories interactive? There has been a lot of research on the topic of interactive dramaturgy, but very little attention has come to the question “why bother?”.
The general engineers’ motivation of “To see whether it can be done” taken aside, there are two main benefits to interactive (and possibly non-linear) stories:
Interactivity gives the user influence in the story. She does not only passively consume the story, but takes part in it. This makes it easier to let oneself immerse into the story world and can help delivering an emotionally richer experience. (see for example [Mateas 2004])
Agency is another term which is often used in connection with interactive stories. It stands for the felt influence on a story (see [Murray 1998], p. 126). I see this primarily as a means to immersion, so it won’t be treated separately here.
Once a story is told, telling it a second time has less effect on the recipient. Non-linear stories offer an improvement at this point. Although the story is similar the second time, it probably (depending on the level of non-linearity) won’t be the same. The recipient does have a hint what might happen from the last session, but she does not really know. The experience has the potential to differ completely. Therefore, a rerun of a non-linear story has a significantly higher appeal than the rerun of a linear story.
The clearest motivations probably come from the gaming industry. Games are interactive. If you add story to games, you have interactive storytelling, so you have to care about it. For games, interactive storytelling is not a new feature that is consciously added. It rather appears naturally.
Non-linear story telling is less common in games. It does have the benefit of increased replay value, but also has the downside of increased complexity.
It should also be noted that the increased replay value is only the positive side of something that can also have negative effects. Especially heavily non-linear storylines can deliver the feeling of having missed important parts of the story. The recipient never knows if he has “seen it all” or whether something has been hidden from him/her.