The Spirit-Filled is necessary for all believing ones.  We live in a world (cosmos) that is the kingdom of Satan.  We live in a world where believers are relentlessly persecuted for the Faith.  Why?  Because believing ones are not of this age (aion).  We belong to the God who gave us Jesus. He is the greatest gift to all of mankind.  He was victorious over the power of sin and the grave.  We can enjoy fellowship with him when we are constantly filled with the Spirit of God.