[aivisol]

I think as it was mentioned in the article it was mostly due to lack of need to travel: they were poor and didn’t have things to trade to justify seagoing. And then the other additional factors: lack of iron, the fact that shores were less habitable than mountains ( lack of freshwater), wind and currents between islands.

[lukan]

But travel between the islands is still something one would think is worth it. And if it is just to prevent incest.

[wolverine876]

Curiosity, or when food runs low, or for a million reasons. And boats are not only for travel between islands; there's also fishing, or to retrieve that thing that washed out to sea in the latest storm, etc etc.