Most financial products come with the warning:
past performance is no guarantee of future results
House prices may have gone up the last 5 years, but that doesn't mean they will this year. From mere facts, we can make educated guesses about the future, but there is always at least an undercurrent of fear because of the uncertainty.
This is what life is like without a preacher, and was the disadvantage suffered by the Gentiles until the missionaries came (Romans 3:1)...
Jews have a preacher, many preachers in fact, and so they have been given God's words. The Gentiles had none, until Paul - Apostle - and thus before the preacher arrived they were reduced to investigating a fallen creation for clues as to who their hidden God was (Paul found them in Athens worshipping a statue that said, "To the unknown God"). Usually God is known by his mighty acts of the past so that even the Gentiles could learn something of God this way. The words that gave Jews an advantage in life were promises by which God could be known in terms of the future...When one is able to trust God by means of a word one speaks very differently to him - in the way husband and wife speak to one another as opposed to the way an advertisement addresses an unknown client.
(pp.54-55, Steven Paulson, Lutheran Theology)
Sadly, many unreached peoples are still in the same situation. Trembling at the sound of a falling leaf (as both Calvin and Luther said).