Jesus didn't want people to know who He really was right away. Which is why demons said this about him:

(Mark 1:24-26 NIV) "What do you want with us, Jesus of Nazareth? Have you come to destroy us? I know who you are--the Holy One of God!" {25} "Be quiet!" said Jesus sternly. "Come out of him!" {26} The evil spirit shook the man violently and came out of him with a shriek.