Palatalization and “strong i” across Inuit dialects

Inuit dialects with palatalization all distinguish between “strong i” and “weak i”: instances of surface [i] that cause palatalization and those that do not, respectively. All dialects that have completely lost this contrast also lack palatalization. Why are there no /i, a, u/ dialects in which all instances of surface [i] trigger palatalization? We propose that this typological gap can be explained using a contrastivist analysis whereby only contrastive features can be phonologically active, palatalization is triggered by [coronal], and contrastive features are assigned in an order placing [low] and [labial] ahead of [coronal]. In a three-vowel inventory only [low] and [labial] are contrastive, while in the four-vowel inventory [coronal] must also be contrastive to distinguish strong and weak i. It follows from these assumptions that [i] can trigger palatalization only if it is in contrast with a fourth vowel.