Jesus wanted to maintain a low profile so he can go around preaching freely.

Mark 1:23-25 Now there was a man in their synagogue with an unclean spirit. And he cried out, saying, “Let us alone! What have we to do with You, Jesus of Nazareth? Did You come to destroy us? I know who You are-the Holy One of God!” But Jesus rebuked him, saying, “Be quiet, and come out of him!”

When the demon tried to speak to Jesus, he commanded it not talk, not because it’s wrong to speak to a demon but He did not want the demon to say who He was. He said the same to leper who was not demon possessed. The instruction not to talk about him was because he did not want attention. The leper decided to testify about what happened as result, Jesus could not enter city.

Mark 1:45 However, he went out and began to proclaim it freely, and to spread the matter, so that Jesus could no longer openly enter the city, but was outside in deserted places; and they came to Him from every direction.

Those doing deliverance often speak to the demon possessed to find out what was the weakness that the person had that created a loophole for the spirit to enter him or her. This is also done so people can learn and avoid same mistakes. Because Jesus did allow the demon to speak, this is often used to criticize those doing deliverance. Those who criticize often don’t do deliverance in their ministries. What does this say about Jesus and his ministry, if he commanded his disciples to go out preaching, healing and cast out demons.

The different gifts are supposed to complement each other for the good of the house of God.