Microsoft is trying to become the default search provider for every Apple product
Next year, Apple's deal with Google for the default position on iOS devices will expire which means that the company is soliciting bids from the big players to see who is willing to pay the most to gain control of this position.
Last week, we saw Mozilla dump Google as the default engine for Firefox and next up, the default search engine for Safari will be up for grabs and it is being reported that Yahoo! and Microsoft are both gunning for this position. With Apple not having its own search engine, it needs to use a third-party for this service which is where Yahoo! and Bing come in to the picture.
Why not Google? Android is the strongest competition to iOS and since Android is run by Google, Apple is helping to boost their bottom line by having Google as the default engine. By taking Google out of the default position, Apple is able to undercut the company's revenue. How much this will impact Google's search and advertising business is unknown but with tens of millions of iOS devices currently set to Google, it could be a sizeable hit for the company.