In the past Comic books were used to show pro war action such as fighting hitler and other world tirents to show that even superheros doing their part in the war would enlist more young people into the fighting effort, not much later there were messages placed within comics to get people to recycle paper and metal to help aid people fighting in the war where they could not help themselfs.Superman was made to show children that even they could be super in their own way giving them freedom in their own imagination of witch clark kent was doing whilst being super man.
At the first age of comics there were no rules in what to published but it was aimed at children over the years it grew slowly into slightly more violance intill the early 90's where drugs, sex and killing came into the limelight with comics such as the punisher and green arrow