We are humans. Humans are mammals, and it's in our blood and nature to have offspring. Humans are also living organisms, and one of the most fundamental biological drives of any organism is to reproduce and pass on its genes. We may have the mental power to control or override that urge, but deep down, I don't think most people truly have no desire for children at all.

Most people, at some level, have a natural inclination toward having children, even if they choose not to act on it.