Every child who has a sense of responsibility will think longer and be useful to his parents as long as he is able to help with whatever is needed without having to deposit money every month. If the child lives with his parents without any strings attached, he can lighten the family's economy by paying for electricity and PDAM bills.
I really agree that this method can help parents in this difficult economy rather than going out on their own, maybe the calculation is more than that.
It's normal for a child that has come of age to offset some responsibilities of his parents so they can enjoy the fruit of their labour. There are some places around the world were this is practice as a thing of been a responsible child and a child who doesn't do it and have the means as irresponsible, this is mostly practice as culture and traditions in many places but to me I see it as nothing. If you are becoming parent and you think taking care of your child means automatic favour in the future, then you have no reason to get married in the first place.
If you have a child and you train them well and you do your best as a parent and give them what they need, you don't need to tell them as a parent what to do. Though, there are some people that you can't change and you can't do anything about it because human being are not the same and they wil shy away from there responsibility and trust me, heaven will not fall. Do your thing as a parent and stop expecting return of favour, that's bad parenting.