Speculations on why medical monitors might be that bright: they can probably be better read in brightly-lit medical settings, shine through overlays and negatives placed over them, and be more easily read by some patients with poor vision.
They also offer palettized grayscale: up to 1,024 tones from a palette of 16,369. I'm not sure how useful that is in practice, but is is a unique feature.
https://www.eizo.com/products/radiforce/gx240/
From their website --
> 10-Bit Simultaneous Grayscale Display
> 10-bit (1,024 tones) simultaneous grayscale display extends grayscale fidelity to the boundaries of human visual perception abilities and helps radiologists discern the finest nuances within an image.