And I totally understand all of that. But if your mapping data comes from Google Maps (which it seems to), and your normal map interaction design is superior (which it seems to be), then why not let everyone use the map features, and roll out things like real-time transit data to cities as you can?
"Our map works best in these cities and the experience isn't the same outside of them" is answered by "1 star, sucks, needs bus data in Ohio".
Mobile apps nowadays need a lot of good will to drive usage, so if any part of the experience is even slightly substandard your users will rake you over the coals.
So, completely reject any user for whom the experience isn't great - it's the rational move. Sadly, supporting your edge cases is harmful to your own health.
You could probably spin something about cheapening the brand with insufficiently awesome experience. Of course the actual reason is probably that they don't want the hosting or support overhead.
Cynically, if the app supported SF no one on HN would care about the rest of the world ;)
