This thread is kind of funny for me because I'm using some of those tropes in my works. 
Like, the fact that the MC of my comic never met her bio-mother and is angsty over it is... well, the reason why the whole story happens. I'd say there's justification for it but I've been always worried if it's strong enough for readers to buy into it
(before the real spoilery reasons are revealed anyway lol)
That's actually related to a thing that really bothers me: never telling the child they were adopted. They only learn, possibly by accident, and maybe even second-hand, as a teenager or adult. drama ensues
I think the reason it's always portrayed so dramatically is because it's a major breach of trust to hide that forever. Yes of course the adoptive parents are the real parents, and I agree 100% that the importance of biological family is overhyped... But a person who was adopted has a right to know about it and should be given a choice to seek contact with their blood relatives, if they want. If nothing else, it might be important for medical reasons. (Though mundane things like that are rarely portrayed in fiction unless it's some dramatic "my child needs organ transplant!" scenario lol.)
It's not even the media as much as it's religion. (the media is this way because it was influenced by conservative/religious values)
In many highly religious cultures, it's believed that a woman's primary, if not only worth is her ability to bear children. So of course a woman who doesn't have them, no matter if it's by choice or not, is seen as having less worth.
Source: I grew up in a very catholic community 
Similar case for me, I have half-sisters in my other WIP who feel extreme hate for each other. Their relationship will eventually get somewhat better though 