In part, because they think they already understand the situation, and the nature of that understanding precludes taking things like that seriously.
“It’s just the flu”
“It only kills 2% of people”
“The flu, cancer, car accidents, malnutrition, etc have killed far more people”
“People were worried about SARS, Swine Flu, and H1N1, and they turned out to be hardly kill anyone.”
“There number of cases here is small. Why are you panicking over nothing?”
“People need to stop panicking. People are going hysterical. The media is trying to make people panic. Just look at them hoarding toilet paper”.
“People are trying to ruin the economy over nothing”
“The experts — epidemiologists — say there’s nothing to worry about” (I’ve had this said to me and I was given a link to a news article that spun statements from some epidemiologists to make it sound that way. They were saying that they didn’t know how the situation would pan out, and this was presented as if it meant they didn’t think there was any issue).
I imagine that most people aren’t aware of the graphs. I imagine most people would be dismissive of them for reasons like the following:
They simply believe the apparent normalcy in front of them more than some abstract maths. They don’t grasp the notion of exponential growth, so it seems fanciful. They also don’t understand how it’s possible to project into the future like that. Maybe they think it’s just fear-mongering speculation. What concrete evidence do they actually have for the situation in Italy? And why should they believe what’s going on in a different country will apply to their country. Maybe their country has a good health care system, and they assume that Italy doesn't.