1. Reaching the lost is central to God's heart:
They key aim in our evangelism is not just to make friends with people, although that great, but to help lead people into a relationship with their heavenly father who loves them. The bible says "The Lord is not slack concerning His promise as some count slackness, but is longsuffering towards us, not willing that any should perish but that all should come to repentance" (2 Peter 3:9) Of course we mustn't just see people as 'projects' we've got to work on, but human beings whom God loves and desires to be in relationship with.
2. The need for US to reach out
3. The closeness of eternity
This is why there is an urgency about the gospel. How many of us have been shocked by the news of the death of someone we knew, or someone we were only just talking with yesterday. None of us know when our time to die will come, that's why we need to be prepared, and why we need to share the gospel message - for as one evangelist put it 'There is something like a too late'!