That's certainly the case in my dad's family - Eastern Europe.
For the person who's asking how they deal with the less pleasant aspects? I guess they just get on with it, hard though it is...but it's a different outlook and they're used to multigenerational homes.
I don't want to go into details here, but I think I've said that I was working full-time and caring for three adults at one point.
I dealt with the messier aspects. Looking back, I sometimes wonder how - but I did it. I'm not saying that others should, just that it's possible.
I also dealt with some aggression and a lot of bewilderment. If it had got to the stage of violence, I would have had to resort to using a care home since I had no other immediate family and I wouldn't have been able to call upon my cousins to help.
But as for how families in other countries cope - and I know that the question was directed at LA2, not me - they get on with it...but there is very much a dependence on family relationships.
Some of my relatives in E.E. live in multigenerational houses built in multiple levels.
I can think of an aunt and uncle who built a bungalow for their newly wed son and DIL in the garden of their home. The last time I visited, my cousin and his family were living in the main house and my aunt and uncle were living in the bungalow.
One of my cousins lived in her husband's family's house. She had a really tough time of it. She was running between her husband's family and her own parents' place. (One of her siblings married abroad; the other - an unmarried brother - lived with her parents. Her husband's sibling had died and her husband was injured in a car crash. Her two sons did as much as possible to help out.) Fortunately, the old folk in both families were compos mentis but there were physical problems.
The last time I saw my cousin's MIL, the old lady was bedridden with severe osteoporosis. The family managed to organise a downstairs inside bathroom for her. She and her husband have since passed away; ditto my cousin's parents.
I do know of one case where a marriage broke up because a young couple argued over which set of parents they would live with.
I'm not saying that this is someone that everyone should do...but it is doable. It can be very difficult, however.