Answer is: money

Young people in particular face a persistently high unemployment rate, while those further along in their careers worry about age discrimination in hiring, in what anxious job seekers call “the curse of 35.”

They also worry about “what their children will face in the future” when it comes to competition at school and in the job market, Tong said.

Make a stable environment and the population will pop up. The $500 year is not enough. You basically need to ablen pay someone a salary to justify having a child.

That’s an easy question: some people still need someone alive around but human children are much more expensive to maintain and with much bigger responsibility. A cat is just a cat. Eats, shits, sleeps, purrs, repeat.