The bug

As of 1.12 an unused illager (illusioner) that was added that renders the hood layer and uses the same texture layout as the other illagers.
As of 1.14, all villagers render the hood layer, but vindicators and evokers still don't.

This hood texture is present in the vindicator, evoker and witch textures too, but doesn't render.
For the witch it was removed again in 19w02a, but the texture for it could've been removed for it instead.

Side notes:
https://minecraft.net/en-us/article/meet-evoker shows an Evoker with a hood, so it should render according to minecraft.net.

Pillagers don't have a hood in the texture (MC-162038), but they use the same texture layout, and for consistency should render them too.

Steps to reproduce: Simply spawn the mobs in question and notice they don't render the hood. The attached resource pack makes sure that pillagers have a hood in the texture too (same area) as well as all others in this report, in case the textures get removed in the future.