In many wedding ceremonies, traditional or otherwise, the bridal couple are facing the officiant with backs to their guests. I was once told that guests are invited to a wedding to serve the couple as the tie that binds them together in marriage.
If the couple experiences marriage stress, it is the task of the witnesses to step in and remind them that they are bound together and are supported by many. It may be important for a couple to face their community of support and join with them as they are joined together.
The greatest wedding gift a guest may bring could well be the later gift of support and encouragement.