Information
In the GUI, both "Install macOS updates" and "Install app updates from the App Store" are dependent on whether "Download new updates when available" is selected.
It is important that a system has the newest updates downloaded so that they can be applied.
Solution
Run the following command to enable auto update:
% /usr/bin/sudo /usr/bin/defaults write /Library/Preferences/com.apple.SoftwareUpdate AutomaticDownload -bool true
Impact:
If "Download new updates when available" is not selected, updates may not be made in a timely manner and the system will be exposed to additional risk.