Maybe because of my status of being married, staying married for a reasonable period of time whilst dodging all the curveballs that were hurled my way in my lifetime (thus far) makes qualified to bless the newlyweds. The family may wish me to part with a bit of wisdom to that effect. Maybe, I, being the eldest in the family, had to represent my recently demised father to do the necessary deeds. He, however, was not a great fan of it either and would scoff all the unnecessary displays of fake niceties and falsehoods seen at these functions. Perhaps, the groom's family just wanted the numbers to show their in-laws that they had the manpower and numbers to defend if accusations of shortchanging or shortcoming should arise.
The ancestors knew that people were the worst of eyewitnesses. That is why a Hindu wedding, unlike others, is irrevocable and irreversible as it was done with the elements of Nature as the presiding judge. The sanctity of the occasion is vouched by the elements of Nature - water, fire, wood, wind. The approvals of the spirits of Nature is invoked through the rituals of symbolism and sounds. For good measure, a camera with its watchful eyes is placed amongst the paraphernalia essential in the cajoling procedure. If onlookers in the human form do not stand up if the sacred union were wronged, leave it to Elements. Offenders to the dharmic order would be dealt with and straightened up in their impartial ways.
The couples' intentions may be private but private intentions involving the privates need the approval of the Higher Forces. Within its act, are disseminated the seed of life. Somebody ought to take responsibility for it. Something so good cannot be without a catch. There is no such thing as a free lunch. Somebody has to clear the mess!