Because there is a higher probability they will earn more and support mama in her dotage.
There is a certain degree of "future investment" when it comes to children in Asia, or at least so I'm told.
Plus a dollop of that good 'ol fashioned Face pretence.
You know how they burn all the drugs in big fires, same, but it's big pile of dongs instead.
Also, this (advancing your career, one dong at a time)
It needs a speech bubble.