Yeah, or it's also possible that your dozen kids would have a dozen kids each and all live on child benefits 
 
Actually, it's not really like that in Canada.  You don't get too much extra money for having kids.  You just pay a bit less in taxes.  You still have to make the money to pay (or not pay) taxes off.  I think the European system is nicer.  The single people can afford to pay a bit more in taxes, they still have a lot left over.  The people with kids need it more.