Why is there so much censorship?

Answer

At what time and where? Censorship has been used for many different reasons in many different places in several times. It was used in the 1700s and 1800s to prevent people talking bad about the government around the world; it was used in the 1900s to prevent demoralising news reach troops and civilians; it is still used in the 2000s to stop people promoting a government or social order other than the incumbent.