I love wedding movies more than I love weddings, and the reason is simple: In a movie about a wedding, you have intimate access to the emotions, resentments, and hopes that are omnipresent, but invisible, at every wedding. Essentially, you get to know how the bride really feels about her in-laws, behind her veneer of Crest-whitened smiles. When you're a guest at the wedding, all you see is the ceremony and the reception, not the drama that's been bubbling up since the engagement. But in a wedding movie, the actual wedding party is just a minor event in a larger, juicier tale.
It's no surprise that so many movies are set around weddings. These unions are joyful, but they're also dramatic. Weddings don't just bring people together; they meld those people's world's together (see: the Royal Wedding). They're occasions for all the significant figures in a person's life to gather in one place, and bring along baggage and expectations, too. All of this is recipe for a good story.