That's because "Friendship Evangelism" IS the way Jesus reached sinners for the Kingdom. Matthew 11:19 and Luke 7:34 even offer this observation from the Pharisees. Where they would have convicted these sinners under the Law Jesus reached them through compassion (offering woes to the cities that did not repent...not because of the Law which they already had but because of the testimony and compassion He demonstrated through miracles).
WOTM is the way of the Pharisees, who condemned man under the Law and expected repentance because of what the Law offered. Evangelism is the opposite. It offers the gospel to a people already condemned - their condemnation made evident through a general revelation (hence man's attempt to reconcile through various religions and philosophies). And God has used WOTM just as He has used other human institutions (such as the Catholic church) - men are saved not because of their erroneous doctrine but despite of it, because within that error the gospel may ultimately be communicated.
Jesus was not the only one doing evangelism in the NT you know.