Every time I set DDG as my default search engine, I return back to Google after two weeks because I get fed up of using !g to get proper search results.
If I know the site where I can get what I seek e.g. Reddit, SO, HN then bangs on DDG are useful but when I don't know which site would get me the information I seek, DDG fails me 9/10 times in giving me a proper result and I have to resort to !g.
DDG needs to be a better search engine first than anything else if it needs to survive, just advertising Privacy wouldn't cut it, Hypothetically If Apple announces a search engine tomorrow most of DDG customer base would shift even if Apple had a poor search engine just because 'Apple sells Privacy better'.