The alternative is going to be a huge amount of caretaking career opportunities.
Paraphrasing a quote from memory: modern society took an integrated solution, then divided it to create two problems.
The original context was something about factory farms. In the past farms were diversified, with animals being raised next to crops, and their waste being easily used as fertilizer. Now it's all specialized and separate: animals being raised at such density that their waste is so concentrated that it can't practically be used for anything; and crops being raised away from animals so they need chemical fertilizers that have to be produced separately.
In multi-generational house, raising young kids is easier because the grandparents can do day care, and being old is easier because the younger generations can help you once you're infirm. Separate that out and you have to pay mega $$$ for all those needs.