It depends on the culture
and where you are.
I work at the study abroad office at my school and I am often tasked to read journals and essays from students abroad. It's often really surprising to read how different the world is out there.
In Costa Rica, most people do not move out of the house until they get married. I looked it up further and yeah, true.
From herehttp://costarica-information.com/about-costa-rica/people-culture-religion/culture/familyIn North America for instance, when children turn 18 years of age, they commonly leave their houses and start living by themselves, but in Costa Rica most children live with their parents until they get married or finish their college degrees. Children who are grown up do not usually move out on their own until they get married, regardless of how old they are. Therefore, it is not uncommon to see families whose children are 30 and have not moved out. There is no negative societal view of this. Just the opposite is true. If a child leaves the house before they are married, it is very unusual and usually only happens if it is absolutely necessary for studies or if the family has very poor relationships.
Same trends exist in quite a few other countries (japan/china). Since most RJers are American, I'm not surprised when people tell you to move out by your early 20s. But really, you should move out when you are financially stable. The problem is, most people don't try to be financially stable until they move out...
Financial stability should be achieved by the time you are in your late 20s/early 30s though... financially unstable guys at that age are kind of a turn off
and perhaps not really socially accepted.