It is important to remember that “annulments” are not favors to be granted or refused* but declarations of facts - as best we mortals can ascertain them - and their consequences. The more proper term, then, in many/most annulment cases is “declaration of nullity,” because the Church isn’t dissolving a bond that already existed. She simply determines that, having done her best to investigate the couple and their circumstances when initial consent seemed to have been given, some defect prevented a marriage from actually taking place to begin with.
The flip side of this is that a dutiful investigation may reveal no evidence of a factor that invalidated the wedding, in which case the presumed validity of the marriage is upheld. But in any case we never move beyond the level of a union’s “presumed” validity, even after rites celebrated according to the Church’s form - the Church never authoritatively declares this or that given marriage to be certainly valid because that validity is subject to conditions we can’t possibly know (intentions of the couple).
*The exception is the Petrine privilege in which a valid natural (i.e., non-sacramental) marriage can be dissolved by the pope in order to allow the Catholic party to enter a marriage more favorable to the practice of the faith. Such dissolution is indeed a favor.
