The main use (as far as benefiting users) for the UID was so that you could install an app on your iPhone, and without ever using any kind of username/password

The main use (as far as benefiting users) for the UID was so that you could install an app on your iPhone, and without ever using any kind of username/password it knew who you were and restored all your data. Of course it also meant ad networks could track you as well. So overall this is a good change, just kinda weird it comes in so late.