Not to misinterpret kragen's excellent points or assign interpretations, but I believe the only surprise you find in this thread is from a biology standpoint. The practice or expressed preference of not seeking to be an "optimal baby making machine" is somewhat not the point in a repr-evo biology discussion, but the phenomenon is curious and intriguing to anyone with a passing interest in the sciences of life. No judgement or opinion emitted, and especially not in matters of social sciences.