My interpretation (which could be completely wrong) is that people perceive a difference between "living with your parents" and "your parents living with you".

My interpretation (which could be completely wrong) is that people perceive a difference between "living with your parents" and "your parents living with you". I think it's a matter of who is the head of the household (i.e. the person who is pulling the most weight regarding the financial stability of the household). So "young adults living with their parents" is interpreted as "young adults not becoming functioning members of society" That said, I agree pretty much entirely with your comment.