Why do we get scared ?

Sometimes it takes a lot of courage to do new things. My nine year old expressed that she feels scared in a crowd of people. Reading up on this some more, I found that it is not very uncommon to develop anxiety because of possible scrutiny from others in a social gathering. This leads to distress and removes clear thinking.
As a kid, I had some social anxiety too. Is this just part of growing up? Is there some concrete ways to deal with this. For me constant exposure brought familiarity. Another way to overcome was to accept the dangers and face them. Best one was to put off the fear and not think about it at all.