Because being scared doesn’t help you. Reality is uglier and harsher than anything we like to admit to ourselves, and yet it’s pointless to be scared since your fear will not protect you. Fear is only useful if it alerts you of a danger you can avoid, but if there’s no possible way to avoid it, if it’s inevitable that it’ll crush you no matter how hard you fight, then what’s the point of being afraid? If you have no hope of survival, what’s left to be afraid of?