However, for Google that makes all its money from advertising, being able to harvest spatiotemporal user data to triangulate purchasing intent must be priceless.
Every time an iOS user interacts with Google Maps, directly or through other apps that use its API, Google gets extremely useful data that soothe its search and advertising pangs, tens of millions of times a day around the globe. For Google (and now Apple) maps are an input modality to discover user intent, perhaps only rivaled by command line search and social network affinity graphs.
But direct financial contribution is not the most important rationale for Google Maps on iOS. One of the key reasons why Google has better data than Apple is the fact that for many years users of Google Maps have been sending corrections to Google, which has improved its accuracy significantly. So by not submitting Google Maps to the App Store, Google would not only give up a very significant portion of its mobile revenue, but more importantly, it would self-induce a debilitating data-blindness on the world’s most lucrative mobile ecosystem.
[And has been asked many times, why is this data not open? Why can’t we all share this to our collective good?]