Whenever I see discussions over not having children, there is a presupposition that having children is the norm--and those who are not having children are actively not having children. I am in a group of "meh". It's just something I don't think about at all, so whenever someone asks me about future kids or hints at my children doing this and that in the future, I'm weirded out and brought back to the reality where I am supposed to be either actively for having kids, or actively ready to defend why I am not having children. "I haven't thought about it" just doesn't seem valid enough an answer.

So, I can totally see why categorizing people who do not want children would prove problematic--there are probably as many motivations as there are people. I'd be more interested in reading a book about why people want children. I'm not saying I'm somehow anti-kid, but I think that people hardly ever really know why they are having children. "It's the right thing to do at this point in my life". I'd love to read about people who actually might have reasons for having children other than wanting to populate the Earth (which I'm sure is not even a top 10 reason for having children these days). It would be fun if both the childless and the child camps would be asked reasonings for their decisions :D