At least in my experience, living with one's parents isn't healthy for an adult.
The are three main problems that people who live with their parents have:
1. They are immature. This is actually very easy to see when you compare students who are living with their parents and the ones who are not. You can argue as much as you want, but when your mom cooks you omelette for breakfast and wash your socks, it's pretty hard to see yourself as an adult (or be seen as one, for that matter).
2. Their parents try to control them. As Cado pointed out, there's a certain dynamic to parent/child relationship and most parents have problems with accepting the fact that you're an adult now. As a result, they lecture their adult kids on how to live, who to date, where to work, etc. That's not healthy to anyone.
3. Their parents are toxic. You wouldn't believe how many people I've met who are broken by their parents. It's not good for anyone's mental health to live with someone who constantly criticizes or humiliates you.
I believe that anyone who had the experience of living on your own and then moving back with your parents or other relatives can testify that living with your parents as an adult is usually not the most pleasant nor the most healthy experience.
I also don't think that the tradition of married couples staying with their parents is healthy. I can't imagine living with a guy and my relatives or his relatives. There would be obvious issues, like mother-in-law, but I also think it's important for young family to have their own space and be a separate "family unit".
I wouldn't want my parents or relatives to move in with me when they're old nor would I want my kids to take me in when I'm old. I don't think it's healthy that most people lose themselves when they have kids and then hang on to them once they grow up, expecting their kids to provide meaning for their lives and then blaming their kids for having their own lives to live. I really hope that I'll be able to let my kids go when it's time and move on with my life.
As for Asians, I personally only heard horror stories about their family ties. I believe there are healthy Asian families, but most young Asian people I've encountered, many of them in this forum, are totally messed up by their controlling parents. Is that healthy? I don't think so.