So, does the officiant have to stand in the middle? No.
I do officiate the vast majority of my weddings while standing in the middle between the bride and groom. They face one another and I face their guests. However, I do move to the side as I pronounce them joined in matrimony for a rather pragmatic reason. I want the photographer to get a direct shot of their first kiss without my red head in the background. That should be their moment alone.
I also move to the side during elements such as a sand ceremony, unity candle, time capsule or any other such ritual. Again this is because I do not want to intrude on any good photo opportunities or obscure the guests' view.
I have officiated a few weddings while standing off to one side, but there is a reason why I typically stand in the center.
One of the most important aspects of my role as an officiant is to provide the "non-anxious presence." I want to make certain the couple are fully present in the moment and enjoying their ceremony. That becomes more difficult if I am off to one side and cannot see their facial expressions or be in a position to communicate via my facial expressions when I feel they need it - whether it be a smile, nod, or even a wink.
I make eye contact with both the couple and their guests frequently throughout the ceremony and off to one side does not allow me to do that quite as well as being centered. Most couples are understandably nervous during their ceremony, whether it is the gravity of the commitment or stage fright generating those nerves. When the officiant is off to one side, the couple can feel totally exposed and the weight of the moment exacerbated, not necessarily in a welcome way. Simply having a calm and reassuring presence within a small circle of intimacy can go a long way in reducing tension and thereby enabling the couple to focus on one another rather than the discomfort of the moment.
Photo Attribute: Cheryl Clermont of Space Coast Photographer