Dystopian fiction is really just the great parts of science fiction taken to their logical extremes. Sci-fi has always been a great vehicle to explore social, cultural, and intellectual issues in, pun intended, a vacuum.
Look at Futurama - many of their episodes deal with modern issues (“Proposition Infinity” being a great example) by extrapolating into the year 3000. Sci-fi tends to pull this sort of thing off to great effect, and the added distance between the reader and the topics at hand can lend an air of freshness and new insight to a long-standing concern.
Dystopian fiction is just a specific kind of science fiction in almost every case, or at least borrows heavily from it. The Handmaid’s Tale is a fantastic book, but it’s also a book about the loss of agency in a possible future marked by exclusionary politics, religious fanaticism, and the decline of the human species as birth rates plummet. These themes are taken in the context of the story, but the mark left by the presentation - a story about the possible consequences of these issues, which seem all too real to some now - is indelible.
If we were to look into it, I think we’d find that dystopian fiction isn’t actually all that popular with the general population. Dystopian fiction is almost inherently intellectual in nature, a study of the human condition under certain circumstances rather than just a good story. I know very few people who are into such endeavors.