People have a tendency to believe what they want to believe, regardless of the evidence they are presented with.  Just one example, the Apollo moon landings were real events that occurred only 50-couple years ago, with many hundreds of people directly involved in making it happen, and many other thousands watching.  Yet look at the sheer numbers today who have firmly convinced themselves that those landings never happened.   

The problem people have with the Bible, is that once they accept it to be true, they open themselves up to being accountable to what it says.  This is why the Jewish leaders had a problem when faced with evidence of Jesus' resurrection.  They had a similar problem after Peter and John healed a lame man.  They knew what happened was real, but tried to stop the information from spreading anyway.

This issue is well laid out in Luke 16:31.  If someone refutes the evidence they have, they won't be convinced by more evidence.