IIRC the reasoning was that if the play store / app store synced, the app would be removed from the phone. I think for the vast majority of people, you may as well ask them to cast a spell as ask them to “sideload an APK”, so if they really really wanted to play Flappy Bird and felt that was beyond their capacity, this was the only alternative. Or maybe people thought phones with the “original” app would appreciate in value as collector’s items? The whole thing is mysterious to me.