@artemis exactly, its like why do so many parents say "you need to give me time to mourn the loss of my son/daughter" to the trans person when they come out. Thats not from any film, its not from popular culture, but it keeps on coming up as a strongly powerful response that parents feel and rather than fight that why take that energy as a lesson of "something is missing here for this person that they need".
In the same way that a parent might cry at their childs wedding because "they're all grown up" etc. Our loved ones need a way for the milestone to be made whole.