1 Peter 2:5 (KJV 1900) 5 Ye also, as lively stones, are built up a spiritual house, an holy priesthood, to offer up spiritual sacrifices, acceptable to God by Jesus Christ.
Why are the lost not won?
All of the lost who are elect shall be won to Christ [Eph 1.4-8], but not necessarily by you.
For the lost to be won, God has ordained two sacrifices: the first is essential: the death and resurrection of Christ. The second sacrifice is optional, my sacrifice of my life for the sake of the gospel. The lost need Jesus, but they do not need me, if I am unwilling to sacrifice myself for the sake of the gospel. God will use someone else.
It is one thing to provide a verbal witness, and scant few do even this. It is another thing to love the sinner enough to give of yourself so that he might be saved. If we are not willing to sacrifice our time, or resources or patience with the lost, why then would God allow us to be the instrument by which they are saved?
The second sacrifice for the sinner is found in the life of the believer who would be used as an instrument by which God saves the lost. Holiness is a sacrifice that pleases God [Heb 12.14], but it also is the means by which the lost are saved [1 Pet 2.12]. A believer unwilling to commit to holiness is an anti-witness. A believer unwilling to spend significant time in ministering to the lost is an unfit vessel to evangelize them. A believer who will not share material things with the lost in order to minister to them is too stingy to be used by God.
A witness is more than a tract. A witness is more than one who can recite John 3.16 to a lost person. A true witness is a sacrifice by which the unbeliever may perceive the corresponding sacrifice of Christ.