Why do they prefer have pets before children?

While  I write this post, I am listening a program of BBC about the couple that they prefer have a pet before a children.

I think it depends where a couple live, in  Spain for example, there are many reasons for this,  I tell you a few:

- A big percentage of the salary of the couple, it spends to pay  the house where they live.

- A child when he go to school, he need books in anothers things, this books changes is very expensive around 300 €.

- When a couple divorce, if they have a child, one member ( usually the father) pays a pension to other member as the other countries of Europe, but in Spain, this drive to the person who pay the pension , go to bankruptcy because he  must continue to pay mortgage apart from pension although he doesn't live in the house who pay him.

But, what do you think?