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I don't have that citation. But Google doesn't spend billions on growing and maintaining apps just for public benefit. Those services pull their weight (now or prospectively) or Google would pull the plug. Generally their strategy is to drive traffic to search, and ads.

It's more subtle than just showing a traditional ad. When you search on a business (i.e. restaurant, hotel etc) in a given area, businesses are often paying to show up prominently in the results and/or when you're zoomed out.

They don't need to. They can show more relevant ads in search or email if they know where you are on the maps.