http://www.theguardian.com/technology/2016/jan/22/google-paid-apple-1bn-to-be-default-ios-search-engine
The payments kept Google as the default search engine for mobile Safari, allowing it to continue to cash in on iOS. And being the default is important: when Apple switched from Google Maps to its own in-house team for the default map app on iPhones in 2012, the new app was criticised for its error-ridden maps.
Three years on, the default app was used three times as much as Google’s own app, according to Apple. That’s millions of users who Google can’t get data from or show adverts to.