The Android Debug Bridge (adb) backup and restore commands may be removed in future Android releases. The command-line tool allows Android users to communicate with Android devices via a USB or Wi-Fi connection. The soon to be added alerts will warn Android users before starting the device backup or restore process that the two adb commands might be removed. Users could either use the built-in Android backup tool (which doesn’t always save all Android and app settings) or root their phones and use an app like Titanium Backup.
Source: https://www.bleepingcomputer.com/news/mobile/google-considers-removing-android-adb-backup-and-restore/