It might be used internally for additional ranking signals. But the privacy policy states it can never be tied back to you as an individual so nothing to worry

It might be used internally for additional ranking signals. But the privacy policy states it can never be tied back to you as an individual so nothing to worry about. From memory the main reason they do this is to allow downstream websites to determine if a user was referred to them by DuckDuckGo without the actual search term. IE you know they came from DDG but with no leakage. I run searchcode.com (which provides a lot of the code doco and sample results) and since this was done I can now determine how much referral traffic actually comes from DDG but have no idea what you were searching for when you click through.