But it's not an either/or proposition. There are sci-fi works that are just in the future without being overtly dystopian or utopian. Asimov's Foundation Series

But it's not an either/or proposition. There are sci-fi works that are just in the future without being overtly dystopian or utopian. Asimov's Foundation Series and the Ender/Bean books, for example. Literature is dominated with dystopia now not just because of narrative possibilities, but because it sells and perhaps speaks to a contemporary world view many of us share. I can't speculate too much on why dystopia is popular, but it's just clearly not just because it's easier to write.