Ep 74: Why do people have children?

The mindcrime liberty show discusses why people continue having more people?  Since the invention and proliferation of effective birth control the  production of children can be divorced from the act to create them.  Before then if people had sex children would most likely result "naturally" in the same way breathing happens. Of course one could abstain but that requires an act of will and self control which for the most part is uncommon.  Since child production in many places is now under the aegis of human action and not merely natural instinct why then do people choose to do so? Is it out of tradition? Is it a kind of hedonistic consumerism as Bryan Caplan describes?  Is it for religious reasons (ie fill the earth or have a quiver full of arrows).   Is it for political reasons in order to continue oneself or ones groups legacy?   What explains the reasons people choose not to do so?  Why is this a taboo topic still? Why is it for the most part so low since the invention of effective birth control?