Aside from a limited set of head queries where they've added their own custom stuff, DDG is a wrapper around Bing. The results are identical and any webmaster can tell you that Duckduckbot is not crawling the web like Google/Bing.
In the same way that "Google is an advertising company", I see DDG as a marketing company. They've done a good job marketing Bing results with a privacy wrapper. I recognize the value, but it's different from competing directly on search.