According to the updated guidelines from Google (via Android Central), Android OEM partners will be no longer required to preload Google+, Google Play Games, Google Play Books, and Google Newsstand apps. It's worth noting that Google previously removed Google Earth and Google Keep as apps that were not required to be part of the Google applications package. The four apps will be available via Google Play and can be downloaded for free if a user wishes. Until now, every Android user who didn't even wish to use these apps had to keep the apps taking up the internal storage space, and sometimes even data. Users only had the option to disable the app from the device's settings page.
One of the possible reasons to remove Google+ from the mandatory app list is said to be Google's efforts to revamp the service completely.
Lately, Google has been refreshing the app policy in Android with the introduction of App Permissions in its latest Android M or Android Marshmallow. One of the biggest additions to the latest Android build was the revamped app permissions. The new feature changes how apps handle permissions, with apps prompting requests for permissions when running which means popups, would flash in the right context and let users grant permissions for specific features. Additionally, users can manage all their app permissions in settings.