For what reason is unknown.
In the seventh beta version of iOS 12, which was released on August 13, there was an important change. From the operating system is missing one of the main new features — group video calls on FaceTime. Apple quickly commented and said that the feature will return in iOS 12 only at the end of 2018.
One of the key features of iOS 12 will be delayed until at least October. Apple hasn’t explained why exactly she had to remove group video calls on FaceTime from the firmware. The company only said that the feature will appear in iOS 12 in future updates at the end of 2018.
Group video calling on FaceTime was removed from the new operating system for Macs macOS Mojave. Thus, one of the most anticipated innovations in iOS and macOS 12 Mojave will have to wait.