When you edit the ticket details for a message, you will be able to see a field for users and groups to include in the message. This is a handy feature to make it easy to quickly add them as you add ticket tags for priority, status and reason. The group you put in this admin setting will be included by default. You can always add/remove users and groups from here when you edit ticket details.
This is especially handy because, using discourse as a ticket system, you want to make sure it is not just one person who is included for continuity and to ensure followup.
All of this said, I don’t use the tickets plugin anymore. There are so many core discourse features for making sure followup happens, including Improved Bookmarks with Reminders and Assigned topic summary for groups.