Parents bring us up, feed us, send us to school, give us money,
give us food and shelter till we go to the working world.
In return, we have to take care of them.
Just like in present, you take care of your children (like what
your parents do last time), so when you old, your children in turn
take care of you.
Everybody will get old one day, if everybody say old pple send
to old folks, then one day, you will also landed in old folks
too.