A lot of people regard their wedding as the most important moment in their entire life, so it's no surprise that there's a large 'wedding planning' market.
Both brides and grooms alike tend to have an image of their 'perfect' wedding ceremony, often wanting to make decisions about decor and scheduling down to minute, seemingly unnoticeable details.
And it makes sense. If you're going to be picky on any day, you might as well do it on your wedding.