Look up filter bubbles[1]. The problem with a search engine that (helpfully) tailors its results to you, and keeps improving that tailoring over time, is that it will cut you off from results that others would see (unless the others are exactly like you). In the short term, having better results is great, but in the long term you are in a bubble.
While DDG does use Bing (and others), the DDG searchers are getting the same results because Bing can't track and tailor your results.
Many also like DDG's bang[2] which easily lets you direct your search elsewhere. For example if you search for "example" and don't like the results, then "example !g" sends it to Google. I like it for slightly more obscure stuff - eg "example !homedepot" does what you'd expect. For us python folk, it is nice to do "example !py2" or "example !py3" depending on the codebase.