For me it's because with Google I don't need to go to page 5 to find interesting results.
I've tried to use DuckDuckGo several times, each time I've quickly found myself trawling page after page of results, reverted to Google and found the stuff I was after on page one.
I've tried to use DuckDuckGo several times, each time I've quickly found myself trawling page after page of results, reverted to Google and found the stuff I was after on page one.