Defining the precise role of a scriptwriter in the videogame industry is not as straightforward as pointing out the rather obvious "dialogue" tip of the game development iceberg. Although scriptwriters are a moderately recent addition to the dev team, their function can be surprisingly widespread, and when properly involved, a professional writer can turn an ordinary game into an extraordinary entertainment experience.
The scope of a game has gone far beyond that of providing an hour or two of twitchy distraction. We're paying three times the price for a game than we do for a movie, so the audience should quite rightly expect at least the same level of entertainment from their Xbox and PlayStation as they do from a cinema screen or DVD player. And herein lies the real gulf separating developers from modern gamers; audience perception.
We're happy to be labeled as "gamers" (and, as opposed to viewers, readers or listeners, it most accurately describes our participation in the experience), yet the person on the end of the controller is still considered a gamer in something of an outdated sense of the matter. Gamers were once a tool of the system; a necessary component to make the program operate as designed and fulfill its purpose as an enjoyable onscreen diversion. But today's gamer, despite his unambiguous categorization, must be regarded as something more than a joystick operator; gamers are an audience, every bit as much as a moviegoer or concert crowd, and demand the same level of consideration.
Most likely, game players are not fully regarded as an audience, due to the non-interactive connotations the word carries with it, yet the inherent implication of a demand to be entertained is something that needs to be addressed. To this end, an experienced writer brings intrinsic abilities to bind the developer and its audience together at a very early stage. When screenwriters begin their task, there are but three concerns: character, story and audience. The audience is the one aspect that's irrefutably consistent.
By including someone who's trained to exploit this particular aspect of the entertainment industry, any medium can find itself much closer to realizing its full potential and avoid the profit-rending "niche markets" as much as possible. Not that there's anything wrong with niche markets, but a well-structured story can transcend its intended, often limited audience and find appeal in a much broader spectrum. This rather specialized aspect of the many entertainment industries is as important as it is overlooked; especially by the game industry.
Of course, the shortcomings are not all on the part of developers who've been slow to acknowledge the necessity of a scriptwriter. The wordsmiths themselves face a problem within their own industry when it comes to writing for games. Movies, books, comics, poetry, magazine articles, web content, even song lyrics all have established, recognized structures when it comes to crafting entertaining literature, yet the method for scripting a game has yet to be fully refined.