This answers the question a little indirectly but here are a few stories from my sibling group.
There are seven children in my family, and our individual personalities have all affected our moving-out status; so have changes in the family (step father lost his business, father's investments started paying big bucks, etc). So the question of when is really personal.
My little sister, now 21, is still living at home. When we talk about it we agree it's right for her to stay at home. She's in school and has a part time job. Personally, I think that's the best thing she could be doing right now and I'm a little jealous of it. My mom could use the help as she takes care of cousins while their parents are at work, and my sister saves on rent and food.
There are 25-yr-old twins. One moved out two or three years ago, the other just this past month (December). The one who moved out a few years ago is much more mature and self-reliant. He's now got a great job that he loves and is in school studying something he is passionate about. The other did some partying and playing, and now he works at a (luxury) bar. Both are happy and getting on with life just fine, but took very different paths to getting out of the house. It should be said that the one partying was living with our grandfather who is rapidly succumbing to age and needed someone in the house. His living at home until he was 25 was important for the family.
When I was 19 I moved out and built up crazy debt because I wasn't ready—I didn't know anything about money. I spent a few years working that off from one lame job to the next. While I don't regret that (I think it was good for me in the long run) I don't recommend it. My budget is to the point now where my spending budget comes within a HK$20 (approximately US$3) each month. Hard-earned results from being a young dummy. Moving out too young (for me) taught me to budget, work hard, plan ahead and manage my life proactively.
I don't think there's a good rule that moving out or not is better for someone, it's all about how the person uses this to their advantage and what their overall situation is.
TL;DR if you haven't moved out yet and you don't have to, it's probably fine to stay at home as long as you use it as a platform to improve your life.