Maybe I don't understand your comment, but I think our societies were/are tighter in many places and epochs. Maybe it's not so in cities and suburbs in the modern West, but, I think it used to be different in Medieval Europe and before, in villages at least. Neighbors were your support community. I know there are parts of the world where it's still the case.
I'm not that old and I was raised by my neighbors, because both of my parents were working. When my dad was dying last year, I couldn't be there because I was their only economic support, working abroad, and I don't have any wealth to be so if I'm not working. There was more family, but the neighbors were the ones day to day helping my mom with shores and the care of my dad.
>> But in any less ideal situations I doubt even the children would have gone out of their way to devote their lives to the care of the elderly or the disabled.
It was the children, in most sane cases. Not that I argue it's a good thing to bring children to the world to take care of you when you are dying.
Did it?
There is an interesting discussion for a picture on reddit's //r/wtf right now: https://old.reddit.com/r/WTF/comments/1ioz5xy/carved_ivory_c...
Basically, it looks like a significant propaganda effort was used to get people to act that way. That means it wasn't automatic at all.
It works best when the parent/child relationship is pretty good, and when the child is not under a lot of pressure him- or herself.
It was the ideal, sure, but how much of it is actually true IRL? There seem to be plenty of bad parents, in which case the children would require quite a bit of pressure and/or brainwashing to take care of them I would think.
And you're too focused on families. This society relied on villages that were all somewhat connected. Modern 3rd world countries still have an arguably richer social support than the US because overall their burdens are not theirs to share alone. They pitch in the care for children, provide food, maintain housing, and much more. Having a big family can simulate this clan feeling but the scale is still a magnitude smaller than a village working together.
>in which case the children would require quite a bit of pressure and/or brainwashing to take care of them I would think.
In the same way kids are "brainwashed" to get kicked out at 18 and make a life for themselves in America with minimum support, sure. Any upbringing can be framed as "brainwashing" if you don't agree with it.