There is a physiological aspect of fear that you would be at a evolutionarily disadvantage without. Without the flight or fight response that comes with fear we wouldn't be able to respond appropriately to dangers. I thing that ff you don't have that response it would probably be due to a genetic illness. That doesn't mean that some people are more prone to fear than others, or that different things trigger fear in different people. I'm afraid of bugs but not snakes but my friend is afraid of snakes and not bugs (kind of a bad example but it gets the point across). I think that there are some situations where everyone would experience fear, but there are also people who aren't fearful except in the most extreme circumstances.