The approach to evangelism that teaches people to share four easy steps to heaven, or the Romans Road, door knocking and easy believism are very tempting to use for these reasons:
1. It alleviates the pressure of the Great Commission for a little while. We as Christians all feel the weight of the world on us when we hear the call to evangelize the world. Going out and hitting up a neighborhood with tracts and door hangers sure relieves that pressure for a little while.
2. It's a guaranteed way to get the "notitia" of the gospel transferred to someone. You can actually say you shared the gospel with someone after having shared the four points of the Romans Road. At least the bare bones minimum of the gospel is transmitted and you can feel good about having shared the gospel.
3. It gives you an easy way to measure your obedience to the Great Commission. If you're like me, you want to measure things to see how they're doing. Door to door soul winning gives you a measurable goal and you can see how well you're obeying.
4. It gives you a sense of accomplishment and righteousness. If you can say you've personally knocked on every door in the city yourself, you'll have accomplished the great commission for your community. Congratulations! Game Over! You will get the soul winners crown!
In reality, it's a mistake to make the great commission about "making converts" or just "go ye therefore". You can't separate sharing the gospel from discipleship as it is so often articulated in Fundamentalism. The great commission is to "make disciples who make disciples" according to Matthew 28:18. So, it's not always something that you can measure as easily as reducing the commission to door knocking. Sharing the gospel is not just giving the information of the gospel, but it is what Paul did by also sharing his life:
1 Thessalonians 2:8 So being affectionately desirous of you, we were willing to have imparted unto you, not the gospel of God only, but also our own souls, because ye were dear unto us.
When you make disciples like this, you're too busy all the time to count doors, numbers and people who prayed the sinners prayer.