I think it is very odd indeed. I don't want my children to be living with me when they are in their 30s. I would feel that I had failed as a parent, in not enabling them to move on as adults.
Yes - working class people did used to live at home until they got married, and then stay with parents for a few years before moving into a place of their own. My parents did this, but they were not 30somethings, they were in their early 20s, which was the norm for their generation.
I work with someone in her 40s who still lives with her parents. Like a previous poster, she socialises with them, goes on holiday with them every year. She would like to meet a man and get married, but in these circumstances, it's not going to happen. She has a younger sister who is married with kids, who finds this relationship with their parents really weird.
And how, unless you are paying a huge amount to your parents for rent, have you managed to run up debts?? 