Weddings are presented as the most important day in people's lives. Personally, I would argue that when the Expendables 2 movie finally dropped was equally important, but that's just me.
Since these ceremonies are super special, and held in such high regard, people expect them to be magical. Flowers floating everywhere. World-class photographers. DJ's who don't hold one part of a headphone to their ear while pretending to live mix the songs they're playing.
You definitely don't want anything dampening the mood and killing everyone's vibe on such a momentous occasion.