You don’t even have to spin it that way. People come to that conclusion on their own, because it is true. In developed countries it costs a lot of money to raise kids, especially if one parent gives up a job to be a full-time parent, or if childcare is needed instead. Things like higher education cost a lot, and often parents have to invest more now to help their kids get fully launched to self-sufficiency in a complex and expensive society. It doesn’t necessarily mean people don’t want to have kids, but sometimes they delay long enough to feel like they are ready (good job, decent house, stable marriage, adequate finances, etc.), that they might actually miss their chance or they might only have the ability to have one or two, even if they would have liked more.