Does the mainstream audience care about all that?
What seduced me was the reasons stated by my grandparent comment (and the fact that good ol' Google search is a "!g" away).
Not everything has to please the mainstream. Discussing whether DuckDuckGo is a good name is one thing. But to questions the features of the engine on account that it's not "mainstream" misses the point. I think.
http://scholar.google.co.in is not meant to be a mainstream product.
Where as http://google.com/search is a mainstream product. And DDG thinks itself as Google's competitor with a heart for privacy, that's their USP.
So yes, as far as DDG is concerned, mainstream matters. It's a generic search engine, not a vertical for scholars or the like.