I have an app which when I tried to install showed a message stating that the author of the app will not allow to install the app in a SD card and will be installed in phone storage.
I want to know why authors of an app don't want to install their apps in SD card?
What is the advantage of installing apps in phone instead of SD card?
I guess there are three key reasons why a developer might choose to prevent apps from being installed onto the SD card:
Sercurity
A SD card can be removed and accessed on a PC which some devs might want to prevent especially if the store sensitive data.
Performance
Installing an app on a SD card adds another variable the developer has to keep in mind especially when it comes to performance. A user make use of a low quality or even corrupted card that can lead to longer loading times and even crashes. A user not knowing this might attribute that faulty behaviour to the app and give it a bad rating in the store.
Unexpected behavior
As Vitor pointed out there are also known issues related to apps installed on SD cards - for example when showing notifications on the Glance screen.
Testing
Testing apps on SD cards does require physical hardware that not every developer might have. Testing on an emulator and just preventing apps from being installed on an SD card is often cheaper.
There might be more reasons, but those are the ones I'm aware of.
