On one side people shouldn’t get special treatment for things of their chosing - that’s just the Principle of fairness of treatment. Nowadays in modern countries with easy access to modern contraception, having kids is a choice. However given how for example in America there is a crack down on abortion, things are going backwards in this and having kids isn’t always a choice anymore, in which case it’s actually fair to more easilly accomodate people who have kids more than people who don’t. On the other side if a country wants to incentivise people to have children in order to, at minimum, avoid a fall in that country’s population, it makes sense to do things to make life easier for people when they have children such as providing free childcare.