In the US it was also a consequence of affluence and lots of living space. A lot of social progress comes when a new generation doesn't have to live within the expectations of the previous generation. The parts of the US where there is a lot of wealth creation are the parts of the US where a lot of young people move to.

So, without making any judgements about how people want to live their lives, I think it is a negative for the US that more young people are living at home.