"Speak not in the ears of a fool: for he will despise the wisdom of thy words." Proverbs 23:9
Ever give advice to someone and they just look at you with a blank look and you know in your heart they'll just go do what they were going to do anyway? This might explain it a bit!! No matter how much Biblical advice you might offer to some, they will never listen. And, that includes the "advice" of the road to salvation. But, we should not give up. You don't know when the door might be open and their heart softened.