because protagonist doesnt want to die? succubus/incubus are actually pretty scary because they eventually suck your life away just like vampires
First of all you're an auto-assassinophiliac. All this "life draining/soul sucking" retardation is a more recent interpretation of succubi that originates from Japan, because this mental illness is very popular there unfortunately. To the Japanese sex is the highest possible achievement, so what better way to die than during sex...right ? They dread returning to their boring, monotone, tedious lives, so they want their "soul drained" whilst experiencing ecstasy.
Succubi went from being seductresses in Christian folklore, that tempt men from the path of righteousness, to predators that kill men by "draining their sperm" or "milking them to death".
Autoassassinophilia is a mental illness, only someone who is mentally ill could be attracted to the idea of dying during sex.
