Fear is needed because we are limited in our mental capacity. Fear is what focuses our limited mental abilities to a task that is needed for survival. Fear is also not optimal, anxiety is literally our fear mechanism failing to work properly. But fear of death is nothing but the need to survive. It is the literal core of everything else. One can even say, it's the only thing needed and everything else is a proxy for it. If survival is all you need, is it wise to expend huge amounts of energy probing the experiences of an ape society?