If you go into the settings, you'll see a list of sources from which they pick stories (you can customize the list).

I think they did this to have an extra thing attracting people to the app on top of pure search. People are likely to spend more time in the app because of it, and thus use DDG for more searches.

You can turn off the stories in the settings and use it as a pure search app, though.

My question for Gabriel & team would be: Is there an iPad version planned?