I started using it 1-2 years ago to decrease the amount of data Google has on me. I still return to Google for some things (unit conversions; searches where DDG's results are unhelpful [Google seems to be more effective when you're trying to buy things]; certain time-based searches DDG doesn't support). When you're looking for a particular meaning of something with multiple meanings or information about a food but not recipes, etc. sometimes one engine will be more effective than the other.

DDG is now my default engine on my phone (where I pretty much never return to Google) and at home, but I still use Google at work.