To the wedding guests, self-written vows are often an excruciating exercise in enduring excessive earnestness. (Sorry, got a little carried away with the alliteration there.) From a performance point of view though, self-written vows are a marvelous opportunity to deliberately inflict discomfort on a large group of people. It’s the one time in the average person’s life that they can hand-select the members of a large audience, have that audience’s undivided attention, and say whatever they want with zero fear of being interrupted.
I’m kind of amazed that most personalized wedding vows don’s sound something like, “I promise to love, honor, and obey, and to treat you with respect and honestly, a marked contrast to how I’ve been treated by my cousin Eric, who is sitting in the third row, and still owes me money from when we were 16!”
If you tell everyone you know that you want to call a meeting of all of your family and friends so that you can say a few things, they tense up, and a lot of them will deliberately avoid the whole thing. If you tell them you’re getting married or renewing your vows, they’ll not only show up, they’ll bring a gift.