The thing is, weddings are only one day!
I think it has a lot to do with the Knot brides wanting the attention focused only on them: noticing how beautiful they look in the gown, having people do other things for you, etc. and wanting their Prince Charming to whisk them away into a carriage. They also seem to have unreal expectations of marriage. It's thought of as a fairytale and once the real work begins, they are stunned and think "the marriage is over!"