Maps, by the nature how we use them for harvesting offline intent, are kind of like a “universal remote control”, which in turn power many other geo-specific apps.
Think about it this way: some people go to the Maps app to start a query or find directions. But many (most?) people use maps / direction from within other apps. E.g. if you look for a restaurant on Yelp in iOS 6, it’s going to use Apple Maps as its default map view. Maybe you initially went in to the Yelp app for its rich experience/reviews/photos etc. When you click “directions to venue”, Yelp closes and the default Maps app is invoked, which is now Apple’s, not Google’s.
And one thing that has gone under the radar during this whole maps catastrophe is the fact that Apple doesn’t allow maps or other default services to be changed by the user. Simply put, there is no setting allowing users to specify the default mapping service. Coordinates / addresses will always open Apple Maps, even if Google Maps were installed. And apps that use maps (Yelp, foursquare, Uber etc) will always use the default mapping service (Apple’s).
This is the very reason why so much hue and cry on Apple Maps. I hope sanity prevails and Apple reverts the decision and better still chooses Bing Maps.