A fundamental tenet of Buddhism is freedom from attachments. If that is so, what is the purpose of the Buddhist marriage ceremony? It seems to be a contradiction, a celebration of attachment within a philosophy that avoids attachment.
Buddhism has teachings for both monks & laypeople. If there were no lay people with worldly attachments, the monks could not be supported with food & other requisites.
Marriage is praised for laypeople, as follows:
In five ways, young householder, the parents thus ministered to as the East by their children, show their compassion:
(i) they restrain them from evil, (ii) they encourage them to do good, (iii) they train them for a profession, (iv) they arrange a suitable marriage, (v) at the proper time they hand over their inheritance to them.
Husband & wife, both of them having conviction, being responsive, being restrained, living by the Dhamma, addressing each other with loving words: they benefit in manifold ways. To them comes bliss. Their enemies are dejected when both are in tune in virtue. Having followed the Dhamma here in this world, both in tune in precepts & practices, they delight in the world of the devas, enjoying the pleasures they desire.
They are just secular affairs in Buddhist countries, and nothing what-so-ever to do with the Teachings. The newly wedded couple and the assembly may recite the Buddha, Dhamma, and Sangha Vandana, the Tisarana and Pancasila at such an occasion. They may obtain the blessing a from monk at the local temple. There are similar Buddhist funeral rites too, but they are all cultural, and nothing to do with the Doctrine or practice.
There are no instructions anywhere in the Vinaya or the Suttas (The Doctrine) as to what one should do at such an event. Whether to marry or to stay a bachelor are personal and individual concerns. You are not duty-bound to do one way or the other. But there are a set of fundamental rituals that have been accepted and followed in a Buddhist marriage.