Because so many, many Christians don't know how to evangelize. They were poorly trained by pastors who went to seminaries that were infiltrated long ago. Anything but the simple gospel! As the Bible says, some demand signs/miracles and others the wisdom of the world, but we are to be undaunted in our commission, keeping our eyes not on the world or ourselves but on Jesus.

The reality of eternal hell is OUR motivation, not theirs, because it's impossible to scare someone into a relationship.