To clarify I haven't seen leather sold from a vendor since Fort Joy area - I am in driftwood. And I check the trade options with every NPC I speak to. The reason I'm confused is that there are some vendors that carry a huge selection such as the arena vendor in driftwood - countless options for weapons, then nothing but plate, chainmail, and robes. There's definitely something that causes it to not spawn leather items that's my question.

Further clarification last leather item I purchased was a unique piece from the dwarf in the black bull inn -only available because it's a unique piece he's predetermined to sell.