Acting is a large part of being a Flight Director. As an example it is recommended to have an artificial intelligence unit, or computer, to help narrate and add extra details to the flight that can sometimes be missed otherwise (i.e. shots during a battle).
There will be other times that the crew may wish to communicate with other ships/stations/planets during the flight. It will be up to the Flight Director to be those other characters with which they have those conversations. This can, for the most part, be done through voice acting or other types of voice modification.
If the resources are available, it is valuable to have actors dress up and interact with the crew during the mission to add to the immersion and story.