All the things you named are things you are doing for yourself in order to have a clean car, to have something to eat, to have clean cloths, to have a dog. Having children is certainly to some extend also something you do for yourself because you enjoy raising children but beyond that it is also a service to the society because this is what keeps it running in the long term. In the past having children was probably more driven by selfish motives, e.g. having someone to care for you when you are old and the like, but nowadays this is no longer true and you can quite easily forgo the costs associated with having children. Therefore it seems not unreasonable to me that a society supports the part of it that takes the burden to sustain it.