Evangelism from the Inside Out

Why is evangelism so important? Christ Himself states in Matthew 28:
Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age. (Matt. 28:19-20 NKJV)
Amen. And in Matthew 9:
Then He said to His disciples, "The harvest truly is plentiful, but the laborers are few. Therefore pray the Lord of the harvest to send out laborers into His harvest." We must prepare workers so the Lord can send them out. (Matt. 9:37-38 NKJV)