What could possibly explain the persistence of these kinds of beliefs (from textbook authors no less!)

Well, a fact about what people in the Middle Ages believed isn't properly in the realm of Physics. I'd expect the physicists to be mostly right about the physics they put in their textbooks, and any other stuff in there should be considered highly suspect.

Consider it yet another exercise in skepticism.

Yes, this sounds more like a problem with textbooks than with science itself.

Textbooks are often censored for political reasons, such as Japanese textbooks' treatment of Nanjing, or American textbooks' treatment of the Japanese internment camps.

This is hard science though, so this won't suffice as an explanation. I fear that people are attached to superstitions about how the brain works. Maybe people like an inaccurately simplified explanation of the brain that claims that specific, local parts of the brain perform specific functions.

We know that fMRI research is pretty sketchy, but even smart people like Sam Harris seem to rely on it too much.

Perhaps most people believed the Earth was flat, while most educated people did not.