Reflective displays have the advantage of perfectly adapting their brightness to their surroundings. This is especially useful for portable devices. Emissive displays can have light-sensor-controlled brightness, but they don't adapt pixel by pixel like reflective displays.

However, if you are using an emissive display in an environment with constant and even lighting, you can set the brightness correctly and it will be just as good. Many people in such lightning conditions configure their displays wrong and mistake the misconfiguration for an inherent disadvantage of emissive displays.

> have the advantage of perfectly adapting their brightness to their surroundings.

The surroundings might not be lit enough for the health of eyes. This is the usual case and one of the prime issues why dead tree books and e-paper tablets lead to weak eyes.

Booklights are a thing.

Cheap, modular, long battery life, effective.

https://duckduckgo.com/?q=booklight&ia=images&iax=images

There's evidence that lack of exposure to sunlight increases risk of myopia. But emissive displays are typically dimmer than sunlit objects, even at full brightness. If insufficient brightness is a concern, you're better off using reflective displays outdoors.

People often read at night before going to sleep. If reading in the Sun was a requirement, one could do that with physical books too. However, most reading happens indoors and for that an iridescent panel screen such as that on an iPad with full gamut of colors is suited better.

[Citation needed]