Why almost everyone obsessed with declining birth rates is a bit weird...

To start it, the people i see complaining the more about it are themselves childless or only 1, everyone i know in real life and online that's obsessed with that is either bc they need new sheep to explore, xenophobic and racist reasons or talk it in a way to shame woman and also queer people about and they also want you to care about it, today i dont know why in my class we are talking once again about birth rates and the teacher put a video about korea and they mentioned that if the korean birth rate stays the same way as now koreans will go extinct in 2750, more than 700 years and i need to care about it? like sorry i really dont care about it