Google.

I've tried to use DDG several times in the past, and while the product works well, Google has the "familiarity effect" baked into its search. I've been conditioned for nearly two decades by Google's layout and visual cues. At a moment when I'm uncertain of something and am searching for an answer, the last thing I want is to be uncertain/unfamiliar with the search tool itself. Those stacking of anxieties, however small, is why I think people continue to use Google.