I don't think it's about expecting care, it's about having the occasional visitor, phonecall, video call, etc. Somebody to give you their news and to hear yours. Just to feel connected to somebody in some way.
I wouldn't want my daughter wiping my arse either- it's not about that. But I hope she'll call me for a chat, visit sometimes, send photos of the grandchildren, include me in family birthdays or other get togethers.
My great grandfather is poorly and with dementia, and seeing photos of his great granddaughter, and hearing about the rest of his family are what he lives for- he can no longer do any of the things he used to enjoy. He's the last of his siblings and has been for 10 years. Parents long dead, all of his friends are dead, his wife dies 7 years ago, and his family are his whole life. Even from a distance. I see the same in patients.
It's not about direct care, it's about having people who you have a connection with. That might be friends or neighbours, but it's much more likely with children and potentially their children in the last years of someone's life.
As I say- not a reason in and of itself to have children, but if you do have children, that's a huge pro.