Why does it seem like so many young people think that they shouldn't have kids?

I can't wrap my head around it. They think that it would make the world more sustainable, reduce some imaginary carbon footprint, make them wealthier than their peers, etc. I don't buy any of that crap. Has no one told them that this fantastic* future means nothing if the people who populate it don't share their genes and their values?

What do you all think on the subject?

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* emphasis on the root word fantasy