I think there are many who have false assurance that employ the Lordship Salvation template of looking for evidence of one’s salvation. First, of all the uncertainty implies the possibility that they may never have believed in Jesus for eternal life apart from their Christian efforts.
But another factor is that they’re belief in total depravity prevents them from acknowledging that God may work through them as unsaved people. (see Acts 10. Esp. 1-6) I think lots of somewhat-Liberal and especially Catholic missionaries stoke a sincere love for Jesus Christ. To me this means that they have responded to some of the light of Scripture. But they’ve closed the door on believing in Jesus for eternal life—that would be too much for many, many people!
I also think if a Bible-believing church-going unregenerate person begins to fervently pray for ministry, that they may see some answer to prayer. Why not? Cornelius did. And there is no indication in Acts 10 that this was unique. Therefore, I see it as a tragic theological blunder to think that clear answers to prayer and God working in one’s life are evidence of being regenerate. And I suspect that many people make this tragic mistake.