The only reasons I can see are
- provide the last GPS position in case none is available at this very moment
- To allow timelapse without the smartphone being nearby. The smartphone tells the dongle the settings but the dongle is controlling the camera.
The problems are clear:
- Nikon does not provide a SDK for Android/Apple
- Nikon does not document the exact behavior of what an app has to do to connect via bluetooth, turn on Wifi, etc.
I would really appreciate that. Ease of use, market opportunities, future developments, cost/margin on your side (app has higher margins than app plus hardware), weather sealing stays intact.