Those millions you speak of are those who are too busy with their own wills and lives, and are unwilling to desire to change who they are by answering the "Knock".
20 Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.
Fits well with: Romans 10:14 How then shall they call on Him in whom they have not believed? And how shall they believe in Him of whom they have not heard? And how shall they hear without a preacher?
Remember "those who have ears to hear, let them hear". Those too busy or concerned about other things don't have ears that can hear what they should hear. So when they read and process the scriptures, all they get is good philosophy, and a world view that doesn't agree with their world view. So then this gets dumped into the void which contains everything else they have no use for.
Romans 1:
21 because, although they knew God, they did not glorify Him as God, nor were thankful, but became futile in their thoughts, and their foolish hearts were darkened. 22 Professing to be wise, they became fools, 23 and changed the glory of the incorruptible God into an image made like corruptible man—and birds and four-footed animals and creeping things.
24 Therefore God also gave them up to uncleanness, in the lusts of their hearts, to dishonor their bodies among themselves, 25 who exchanged the truth of God for the lie, and worshiped and served the creature rather than the Creator, who is blessed forever. Amen.