As a simple example, think of how many people you know who are afraid of flying. Then think of how many people are afraid of riding in a car. The latter is far riskier per passenger mile. I think part of this has to do with familiarity.
The single question I get asked most often about travel in the developing world is whether I'm afraid of getting sick. Yes, tropical diseases do pose some risks that I am less likely to be exposed to at home. But I can get the recommended vaccines, take anti-malarial drugs, and take other reasonable precautions (e.g. drinking bottled water and, ideally, fizzy water as it's less likely to be repackaged tap water). The far greater risk comes from taxi drivers and bus drivers.
You can't get the risk of anything down to zero. Staying home with your door locked won't help either, given that you can just as easily slip in the bathtub and hit your head. The real question is how much risk is acceptable. Each of us has to choose that for ourselves.
Me, I draw the line at active war zones and, as much as I like bears, I'm not about to climb into a cage with one.