This is an interesting topic that I have been thinking of a lot.
Both my parents are fine financially. My dad is 73 and mom is 70. However, they have made NO plans for this at all. They live in the house I grew up in and could not physically separate themselves from it. My mom hoards clothes and dad has his garages (yes plural) full of stuff. Me and my siblings live 1000 miles away and they don't think of this as a problem. My mom is not great health-wise (bad neuropathy so falls easily). I would love to see them in this type of living as it would keep them more active with peers and not so sequestered.
Then there's my SO's mom. She's 74 and would love this kind of living. The only thing is she could never afford it. She never saved for retirement, had menial jobs, was a single parent, and now lives in a condo that I own but pays me rent that just covers taxes and HOA. It sounds like there might be some options for indigent people, but she's not yet in need of a nursing home.
This is where I would love to compare the US versus some other industrialized country like Germany or the UK. We pretty much just turn our seniors out and see if they can survive on SS alone. Her SS barely covers rent and medicines.