Not only does God and His angels want us to witness to the lost, but the residents of hell are crying out for someone to witness to their lost families and friends before it's too late. What an awesome responsibility we have. God could have used powers and principalities to witness, but He gave man this great opportunity. He confused poor Nicodemus about the water and Spirit birth. An angel could have told the Ethiopian Eunuch how to be saved, but Phillip was directed to attend to this need, and carry the message to the desert.
Man telling man how to be saved is the greatest deal around.
Yet, he was directed to talk to a man about God's plan of salvation. Brother Ananias was given the privilege of telling the plan of salvation to Paul. Think about his downline credit for this Network sponsorship of the greatest soul winner ever. Cornelius was given several visual signs and Peter was given a type of video presentation just to get these two men together. God again allowed man to tell man the saving plan for souls.