- they're dim (in comparison to an otherwise equivalent display)
- they don't showroom well (because they're dim)
- marketing them is difficult --- not many folks are willing to pay a premium to avoid the need to do the "hipster dance" and shade their screen (or just wait a bit to use their device)
The ideal would be for a retailer to set up a daylight viewing booth in all their spaces (expensive) and then convince folks to test/compare devices in what is essentially a suntan booth (health implications).
I wish that someone would revisit the Lenovo Yogabook which had a secondary e-ink display as keyboard/drawing area/e-ink tablet as a reasonable compromise.
EDIT: I will note that there are (or were?) some such devices available from specialty suppliers for nautical use, or in rugged devices intended for use on construction sites.
They were okay, each eye would receive a slightly different image due to the poor viewing angles of the 2010 tech.
It would be really cool if someone made a modern version that fit into a standard laptop housing: eDP 30/40 pin + 14.0" / 15.6" / etc.
What benefit do I get from turning off the backlight? Battery life? Why do I need that when batteries are so cheap/abundant?
It's far easier to just toss in a big battery. For example, the Odin 2 is a handheld gaming device where you can get about 8 hours of battery life playing extremely demanding emulated games like PS2 and GameCube, or play longer than you can stay awake with older games like Super Nintendo or Game Boy Advance.
Or look at your typical PC or Mac laptop, these devices are going the entire workday with the backlight on with no problem.
And of course you'd get even more run time with an external portable battery.
These devices are clever but just make less and less sense over time as our more prevalent technology improves.
Plus, we have more panel choices in the traditional space than ever. Mini-LED devices are fantastic in bright sunlight because the backlight is just so powerful. OLED is incredible for contrast and great color quality and accuracy.
What is transreflexive offering over those solutions?
Maybe this is perfect for "beach reader" ereaders.
So it is better to make either a purely emissive (OLED) / transmissive (LCD) screen, or a purely reflective screen with an added front light.
And why are there so few devices with reflective LCD screens? They are quicker, but they reflect less light than the electrophoretic screens from E Ink.
If somebody invent cheap lcd without electrodes on cover glass (may be all electrodes on back side), things could change, but for now people buy lcd because of cheapness.
Unfortunately, most reviewers seem to have completely missed the point of the device. If you want high contrast and color accuracy, use an OLED. If you want to read outside in the sun, use e-ink.