The obvious reason is you can't make up the stuff in the news these days. Our dystopian future is here, right now, so there's no better place to look for writing prompts.
But another reason is this; /r/writingprompts.
Not long after discovering Reddit, I found the Writing Prompts subreddit. Good dystopian prompts were thin on the ground, but I found a decent one most days, which got me into the habit of banging out 500-800 word shorts (like I do here).
Then one day I saw a news story online that I thought would make a good prompt; the Ku Klux Klan was reportedly opening its doors to black members. If there was ever a dystopian writing prompt crying out for attention, this was it.
So, being the responsible Redditor I was, I read all the dos and don'ts (there's quite a few), and submitted my first prompt. It looked something like this:
[WP] The KKK has opened its doors to black members. You're black, and you join up. What happens at your first meeting?
But a funny thing happened; it didn't appear. I waited. I clicked the "New" tab. I waited and clicked some more. Nothing. I wrote to the mods asking what happened. One wrote back. He said he'd deleted it because it was too controversial.
That was a couple of years ago. I kept on writing and posting, but that response nagged at me. Eventually, I deleted everything from Reddit and deactivated my account.
If you want to control the way people think, get a job at a mainstream publisher like Tor. Reddit is converged. I'm better off doing my own thing on a blog.
Besides, writing prompts from news sources beat the hell out of the stuff they get on /r/writingprompts.
UPDATE: After I posted this, I started watching a Periscope by Vox Day, titled "Reddit ban, Twitter crackdown, and the revival of heroism". It's related to what I've written here, and well worth your time. It's excellent.