Why do you think we fear what we don't understand?
Rationally speaking, isn't what is unknown neither more or less likely to be harmful to us?
Ah, but if survival is the greatest desire, we know what is familiar to us is already safe. You don't need to eat funny looking berries until you're on the brink of starvation.
However, compared to before we are already relatively safe. Those with an unfair share of negative experiences are even less likely to explore what is unknown because they expect more of the same, which is ironic because that is exactly what they need to do to find the good they have been missing.