Why didn't Jesus want the demon possessed people to tell who he was?

So Jesus healed great numbers of sick people who had many different kinds of diseases, and he ordered many demons to come out of their victims. But because they knew who he was, he refused to allow the demons to speak. Mark 1:34 NLT > So Jesus healed many people who were sick with various diseases, and > he cast out many demons. But because the demons knew who he was, he > did not allow them to speak Mark 3:12 NLT But Jesus strictly warned them not to say who he was.