Some people when they get old require around the clock care for their health, safety and well being and caring for an elderly parent around the clock just is not possible because the children who are now adults have their own lives to live and have jobs that they have to go too.
I've helped take care of my Grandpa and although I loved and still love him even though he's gone now it was very hard to take care of him and dragged me down.
I would not want my kids to have to take care of me in my elder years if I got to the point of needing nursing care and I would rather them put me in a nursing home or at least have a home health nurse take care of me.
Some people though will just try to get their parents into a nursing home when they get old so that they can get rid of them basically and take their things before they die which is sad.
But some people really do need to be in nursing homes especially those people who have dementia and cannot care of themselves.