Unfortunately most people are selfish and only adhere to morality because it is beneficial. So in a society that is very poor a person has less to loose when the don't act morally in fact the will mostly are concerned with their continued survival if morality helps them survive they will adhere to moral standards. In a developed society morality is optimal because you have more to loose from acts of immorality. Morality also contributes to a stable society. Sexual morality is a different matter less developed countries tend to be less permissive of sexuality because sexuality is used to consolidate power and authority in a society with less development. These societies however are more likely to be more permissive of violence and abuse of human rights. In my mind its hard to argue that sexual promiscuity is more immoral than unjustified violence.