The answer is quite easy but unreasonable.
They are busy managing their own lives and jobs and families, and have less time to take care of their parents.
I don't understand how they can be so unfeeling in this issue. If they are busy, at least they can hire a person to come to their home to take care of their parents, not to send them to nursing homes. In my opinion , it's not fair at all.
After all the troubles, the parents have suffered for raising their children, it's not a good way to thank them.
Maybe some of you disagree with me, but at least you can admit that it was really a controversial topic......