I find it interesting that those who don't want kids _must_ supply a reason, while the opposite isn't true. I'm at the age where all my friends are having their first and second children, and absolutely none of them had to give an answer to "Why?" If you plan to have kids, the only reason you need to supply is "because I want them." But people who don't plan on having kids tend to explain in a multi-part essay about their economic hardships, lack of time, and existential listlessness. I assume this is because people (especially potential grandparents) don't accept a simple "I don't want kids" as an answer.