Mark 5 & 6 – in verse 18, why didn’t our Messiah let the man who was demon-possessed accompany Him?

Mark 5:18
And as He was getting into the boat, the man who had been demon-possessed was entreating Him that he might accompany Him.
Mark 5:19
And He did not let him, but He said^ to him, "Go home to your people and report to them what great things the Lord has done for you, and how He had mercy on you."
Mark 5:20
And he went away and began to proclaim in Decapolis what great things Jesus had done for him; and everyone marveled.
This man was apparently not from that area, but was from Decapolis. Why didn't Jesus let the man be one of His disciples? This man wanted to glorify Elohim. Yeshua knew the best way to glorify the Father was for him to display himself as being cured to those in his hometown.