In every fairy tale there is a hero. The hero shows great courage in going after and defending his love. The heroine relies on her hero. Those facts underscore the reason why a fairy tale theme could rightly become part of a ceremony that defined the marriage of two adults.
Prior to any wedding ceremony, the groom has become the hero for the bride. The bride will spend her life looking to her husband for love and support. The bride will be a heroine for her husband. The husband will work to support and care for his heroine. Two adults, who have agreed to take their wedding vows, have really agreed to live out a sort of fairy tale theme.
The bride does not expect her husband to have a mind clouded with wedding fairy tale dreams. The bride counts on her husband to stand-by her in times of trouble. The bride knows that she too must be ready to stand-by her partner. In a religious wedding ceremony, the bride and groom both understand that they will rely upon God as they confront their problems together.
At any wedding ceremony a bride and groom have no way of knowing what problems they might have to deal with. They might, for example, find that they need to seek help with starting a family. They might find that one of them develops a disease or other physical problem. They might find that one of them suffers persecution for a religious belief or a family tie.
Any of those problems would call for the courage of a hero and a heroine. Any of those problems would focus the attention of friends and family on the battles that a couple must fight together. Any of those problems would most certainly illustrate the reason why a couple might rightly choose to have a fairy tale theme at a wedding ceremony.
In fact, the presence in a marriage of such problems does not need to diminish the strength of the relationship that led to the wedding. The presence of such problems emphasizes the appropriateness of a religious wedding ceremony. Such problems require the making of choices, and the making of choices helps the spirit to grow stronger.
Perhaps that is why religious institutions play an important part in many wedding ceremonies. Perhaps that is why even wedding ceremonies held outside of a House of Worship often include sacred verses. Perhaps that is why young parents with children often use fairy tales to teach their children about good and evil.
Many romance novelists have noted the appropriateness of a fairy tale theme at a wedding. Many of the young females who read those novels have noted their frequently-repeated ending. Many romance novels end with the hero and heroine making plans to stand before the altar, or to otherwise become man and wife.