Censorship is necessary to avoid offending certain people. Certain things that may be considered offensive to a group of people, whether it's by race, religion or political beliefs, have to be censored to avoid offending the moral values of others.
Censorship is necessary to avoid offending people, and is also necessary to avoid exposing people of certain age groups to particular things that may be unsuitable for them. This may include music or images. Due to censorship, certain music albums containing explicit lyrics must bear parental advisory stickers on the covers. Movies must provide ratings that tell the viewers about the appropriate age groups that may watch certain movies, as well as warning viewers about potential content that they may find objectionable, especially in terms of inappropriate content for younger viewers.
On terrestrial radio, censorship makes sure that any music being played is a clean version of the song. The same thing applies to certain movies that may be broadcast on television. Instead of broadcasting the explicit version on cable television, an edited and censored version is shown instead. This form of censorship allows things to be broadcast to a broader audience with a lower chance of offending the viewers.