In this instance it seems that the practice was the ideal time, to sort the issue out before there was a problem at the actual ceremony. (religion.blogs.cnn.com)
The event - a pre-wedding bash that also allowed the couple to celebrate with a larger crowd than will be at their actual ceremony on Long Island next weekend - had about 300 people, per The Post, including much of the New York delegation and Bill Clinton. (politico.com)
That tradition actually came from the olden days of arranged marriages when the groom wouldn't meet his bride until the actual ceremony, so there would be no turning back. (medicineandmanicures.com)