The fact is that Apple and Google had a five year agreement, not entirely unlike the one Apple shared with Microsoft from 1997-2002, where steady updates of Office to the struggling Mac platform were promised. People worried that Apple would suffer with the prospect of Microsoft letting Office die on the vine at the end of that term, but the reality is that both companies continued to create and update products that fill that productivity need, and users today have great choices with Office 2011 and iWork.
No one outside of Apple and Google knows the particulars of why the companies completely parted ways with Maps on the iPhone. The common assumption is that it was entirely Apple’s move to protect its platform from a rival, but we don’t know. Perhaps Google decided to pull the plug to protect their own platform, or maybe they wanted to junk up the built in YouTube and Maps apps with tons of ads, and Apple balked.
Most importantly for Apple, they are no longer depending on Microsoft to stay relevant. Five years into iOS, they are (or were) pretty reliant on Google for a core part of their user experience. I predict that Apple Maps will improve rapidly and Google will eventually have their own solution in the iOS App Store, complete with all the ads they want to sell. The new YouTube app does that now. I don’t think Apple would reject a Google maps app considering Mapquest has been available for a while.