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.
Isnt it very personal and geographical question? I cant remember correctly, but there are countries where it is common for children to leave parents house when they turn 18. It will even look weird if children, who are adults now, live with parents. And there countries where it is normal for parents to support their children as long as children want. So it is ok to see a 25-30 years old who live with parents, that pay all the bills and feed their child.
I personally look on this situation in first post from how the kids and parents were raised and financial situation. Imho if children are smart, they will understand that they "should help" parents cover expenses. But I see it wrong if parents say that there is a specific amount (like $75/month) to be paid and it is a must. Parents should to plan in the beginning, that children would not be obliged to share expenses. Because they did not give birth to create a person who will cover 1/3 of their expenses.