I recently ran across a book called The Highly Sensitive Person. While it's not a childfree book per se, it applies very well to me and touches on a lot of the reasons why I don't want to have children.
The basic theory of the book is that some people are highly sensitive people (HSPs), and as such, are more easily overstimulated than others. I am one of them. For example, I'm likely to crave a return to a quiet home after a stressful day at work, rather than continuing on to drinks with my coworkers. I'm likely to close the door of my office while working, because the noise from the hallway bothers me. I keep my windows shut at home to keep out the street noise. I'd usually rather have silence than listen to music when I get home. I hate being interrupted by chatter when I'm trying to do something, even if it's just writing a blog post. It becomes very hard for me to concentrate.
You get the picture. According to the book, 15-20% of the population are highly sensitive people. These people tend to be introverted, and although we like stimulation, we like it in small, managed doses.
Does that sound like a person who would deal well with a screaming baby to you? I know I wouldn't, and that's part of my reason for remaining childfree.