It's part of a bigger trend that MS is engaged in to move most of their apps to the App Store: Mail, Feedback Hub, Calendar, Maps, etc, are all in the Store. It

It's part of a bigger trend that MS is engaged in to move most of their apps to the App Store: Mail, Feedback Hub, Calendar, Maps, etc, are all in the Store. It makes updating one of the apps separate from updating the OS (and Windows Update). This is a net positive move for consumers, I think.