I've noticed you post about kids a lot. I'm curious as to why.
As for the question... people might want them because it's way easier and often more fun to be able to interact with nephews and nieces than their own children. You can have all the fun of having kids around with none of the responsibilities that go along with having your own children. My oldest daughter has no kids, my middle one does. My oldest loves seeing her nephew. He comes to visit her, they can play, she can spoil him rotten, then she can send him home and she gets to kick back and relax and do her thing again. She doesn't have to stress school, bedtimes, health issues, nothing...it's all fun until she's ready to send him home again. As far as she's concerned, it's all the perks, none of the hassles.