what is the purpose of the Buddhist marriage ceremony? 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 &amp; laypeople. If there were no lay people with worldly attachments, the monks could not be supported with food &amp; 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.
  
  Sigalovada Sutta


~~~


  Husband &amp; 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 &amp;
  practices, they delight in the world of the devas, enjoying the
  pleasures they desire.
  
  Samajivina Sutta