So why don't you just watch movies and TV?
I like movies ... TV I'm not so sure about, although there are good programs out there.
The problem with movies and TV is this: they cost a lot to produce. No, let me rephrase that -- they cost an astronomical amount. Apart from the indie movie scene, which tends to be perpetually marginalized, no one individual can make them. They are group efforts, and while this gives them some strengths, they suffer from the near-inevitable tendency of group creations to lose any singular voice. And it's the singular voice that has to survive. It's the individual consciousness, not the group, that maintains contact with life.
And this is one of the great strengths of books: because they're relatively cheap to produce, they can still be made by individuals. (The contemporary trend toward "packaging" a book is pernicious on so many levels, as the Kaavya Viswanathan incident showed. If this scandal will be enough to stop the general trend to package books and turn even them into bland, committee-made products remains to be seen.)
Mass culture, with its converging technologies such as TV-receiving cell phones and ubiquitous WiBro reception, keeps moving more and more toward post-literacy. We are in desperate need of narrative forms that both can reach an audience but also allow the artist to retain his or her individuality. The screenplay-novel is a way of "writing a movie".
The screenplay-novel is not a selling out. Think of it this way: there are good movies. There is good TV. In other words, both mediums are capable of producing genuine works of art, despite their group-made natures. If you write a screenplay-novel, you should try to make something that also has artistic merit. Obviously, it won't have the linguistic, descriptive power of great novels. But it will have the capacity to stir people's imaginations.
And when reading a screenplay-novel, all people have to do is allow themselves to read it as a director might. This is one of the broad-based effects that movies have had on the modern mind: it is possible -- even natural, it sometimes seems -- to think "cinematically". In other words, our minds have already been conditioned to imagine narratives as if they were movies. Maybe everyone doesn't do this. But many people do, and they do it effortlessly. In this sense, we are all directors now.
The trick is to be a good director -- an auteur, if you will. Remember that the best movies and TV are often made in opposition to mass culture. The screenplay-novel is another way of doing that.
But what about reading? If everyone is "being a director", won't reading suffer even more?
People are still reading lots these days. The trend among readers, however, is to buy more non-fiction than fiction.
What's wrong with that?
Nothing in the sense that non-fiction has always been popular, and now simply is more so. However, we still need fiction. It's not a luxury. It's a necessity, as well. Cultures rise and fall based partly on the stories they tell themselves.
I think screenplays suck. Traditional novels are more interesting to read.
Then read traditional novels. But consider the possibility that the screenplay-novel idea is a relatively new one, and part of your antagonism to them may be the result of being conditioned to read fictional narrative one way and not another. Remember that: the screenplay novel is just another form of narrative.