"Faith comes from hearing the message, and the message is heard through the word of Christ." Rom 10:17 God has made the Word of God the essential source and object of faith. Faith in the Lord Jesus, the Word made flesh, is engendered in faith in what Jesus said. Sharing one's lifestyle does not constitute "evangelism". If the Word of God has not been communicated then Salvation is not possible. If the seed is not planted, no fruit should be expected.
Furthermore we are talking here about God's Word, not man's word. Charismatic elements in modern Christendom as well as dogmatic traditionalism have developed misconceptions concerning what constitutes "the Word of God". I have heard preachers imply or even directly declare that their sermons should be reckoned the infallible Word of God not to be subjected to scrutiny. Whereas often in such sermons the Bible is scantily quoted and often misapplied.