Siri and Spotlight Use Google For Search Engines

Google on Siri
Apple no longer uses Bing as a search engine for Siri search results in iOS and Spotlight on macOS. Instead, Apple uses the Google search engine. This change has started rolling on iPhone and Mac users.
"Using Google as a provider of search results on Siri, Search in iOS and Spotlight on Mac makes these two services can provide a consistent internet search experience, just like Safari's default," Apple said in an official statement.
Apple still uses Bing as the default search engine to perform image searches on either Siri or Spotlight.

Video search will still be handled by YouTube. Apparently, Apple's reason for rolling this change now is because today coincided with the launch of the Sierra High macOS.

The reason Apple took this step is because Google has paid billions of US dollars to keep it into the main search engine on Apple-made devices.