Exactly, we have lots of instances of other parts of the body becoming infected but brain sicknesses I think go untreated probably because they are hard to detect and the brain is so resilient.
I think it's a combination of it being difficult/expensive to get inside the brain, limiting such exploration to only the most severe cases, and also a latent bias in western culture to buy into Mind-Body Duality. The idea that the Mind is separate from the Body is still prevalent, and has an insidious effect on many people's judgement: even people who are trained otherwise.