What I meant is if a typical woman of today would have a choice to join society A where she gets maternity benefits or society B where everything is handled by the market, she would choose A. Free to choose! 
In a free society, you should not be free to choose how to spend other people's resources.
But anyway, I don't deny that people tend to seek places where they can better externalize the costs of their actions. All I'm arguing is that (1) it is unethical and (2) economically sub-optimal.
Once I saw something about young French citizens (men and women) who would live abroad during their youth, in places where they'd pay less taxes, collect more money, and then, when they were feeling like starting a family, come back to France where they'd get many benefits for having their children there. In other words, when they are fully productive, they search the place where they get to retain more the results of their labor. Then they come back and eventually some even become a burden to society. You don't need to be a genius to figure out that's not really a good deal to the French economy...
maybe I merely mean to say that libertarians and anarcho-capitalists have to try harder to preach their gospel.
That's likely true.
But honestly I tend to agree with Patri Friedman when he says that we spend a lot of effort on "preaching", and if instead we'd spend more effort on "acting" we'd get better results.