The problem is a lack of firsthand experience.

If your experience with polio is nonexistent, it's easy to dismiss "1 in 1000 people suffer from paralysis" as a small fraction of cases without considering the horrific reality of that paralyzing thousands of people in a city of millions, to say nothing of the other effects.

This is also, I think, related to why doctors are often dismissive of patient concerns - our expectations have shifted, because so few things that occur frequently require active intervention to reduce mortality any more, comparatively.