Why have they never left the island for thousands of years?
I just fail to understand how they maintained so minimal contact with the outside world for thousands of years and stayed primitive. It just doesn't align with how human societies are expected to behave and even in pre-historic times primitive humans kept migrating and moving around to other locations for various reasons, food, meeting other peoples, discovery or sheer curiosity. In fact, the only thing that kept humans in place was some degree of civilization and advancement. Primitive humans are supposed to move around as nomads, the same way animals do.
I just think something's off here. Their island is not so far off the other islands or the mainland where they could be exposed to some civilization. They are supposed to KNOW that other peoples exist too, and other places too, since they got visitors from time to time. Do they not want to discover what is the source of some different people coming in and in big ships? Why do they seclude? It just doesn't make sense to me.
I'd suggest that there could be some sort of a deeply ingrained belief in their culture or religion of some sort, that leaving the island would curse them, so they are not permitted to, and maybe the big chefs do not allow anyone to leave as they are strictly obedient to these beliefs and all.
I'm just wondering the psychological aspect of this. "They want to be alone" is not the answer as we know from history that humans moved a lot even when they were primitive. I'm just contemplating on why they are not curious, not want to discover other places, or just do not want to migrate.