iOS is becoming more open to third party service integration, anything that is not from Google
Initially, the iPhone was heavily reliant on Google services such as Google search, Maps and YouTube.
Over time, Apple has slowly but surely started integrating often competing non-Google services and other apps. Bing was offered as a search option, Twitter and Facebook integration became deeper and for China local services took over. Siri has also grown on it, and is becoming a bigger part of the iPhone experience.
Mapping the trends in iOS apps, below is an interesting graph that illustrates the departure from Google apps and the growing number of third party services in iOS. Check it out.