DuckDuckGo has made its name on being the "private" alternative search engine. It has gained most of its users by promoting itself as an alternative to Google that will not track you in any way, and its inclusion in Safari for iOS could serve to see its market share grow. It may not be a huge bump though, because users will still have to go into settings to actively change the search provider in Safari, and many users (regardless of platform) tend to stick with defaults (as evidenced by Google Maps on iOS dropping from 81.1 million users in September 2012 to 58.8 million in September 2013, according to comScore).
Google is still the default in Safari, and users can use Google in Siri, but more choice is always nice, especially if you aren't a big fan of Bing or Yahoo search. And, more choice seems to be an interesting theme with Apple's latest update, which has been surprising many users.
source: The Verge