I think it's important to have closure in any relationship that ends - from a romantic relationship to a friendship. You should always have a sense of clarity at the end and know why it began and why it ended. You need that in your life to move cleanly into your next phase.
One tradition I have with my friends is that when one of us gets married, we have a ton of fragrance oils and pretty bottles at the bachelorette party. Everyone puts a drop or two in a bottle for the bride and makes a wish, and the bride wears our creation on her wedding day.