Fear is a vital response to physical and emotional danger which has strong roots in human evolution. If people didn’t feel fear, they couldn’t protect themselves from legitimate threats, which in the ancestral world frequently resulted in life-or-death consequences.
In the modern world, individuals often fear situations in which the stakes are much lower, such as public speaking, but their bodies and brains may still treat the threat as lethal. This can trigger an extreme, although often unnecessary, fight-flight-or-freeze response. As a result, people may find themselves avoiding challenges that could benefit them in the long run or hanging back during social interactions.
When people today do face deadly or extreme danger, it can sometimes cause lingering trauma. Such trauma can trigger a fear response that is hard to quell, even when the risk has passed.