Luke 15: benefits of evangelism, why evangelism is important

Luke 15 vs. 7, 10 - 7 I say unto you, that likewise joy shall be in heaven over one sinner that repenteth, more than over ninety and nine just persons, which need no repentance. 10 Likewise, I say unto you, there is joy in the presence of the angels of God over one sinner that repenteth....