I agree with the last answer. but also some other and common reasons are because people have the choice to move there or move away, because some people are born there and enjoy their lives there, or, like i already said, because of the examples given in the last answer. :)
That statement is true
Despite its importance, what actions that could be considered as a crime actually really subjective depending on which society that you lived in.
For example, hitting your wife in united states will definitely result in prosecution while in some part of Asian Region, it actually considered as socially acceptable behavior