Being reflective or emitting has nothing to do with use of e-ink in e-readers. Main advantage of e-ink displays is that they only draw power when the display is updated, they don't consume any power to maintain the image unlike LCD or OLED displays which makes them a lot more power-efficient. However with every e-ink display having a mechanical component (little ink particles are moved around by electric fields) their refresh rate is relatively slow in comparison to an LCD or OLED which makes them unsuitable as a general purpose computer display. Since e-reader display mostly static content (text, no animation) an e-ink display is perfect for that purpose, offering much lower power consumption.

Yeah... so last century. I wanna see this done in Javascript.

Also reminds me of Twilight or Gloom concept from the Watch trilogy (Nightwatch movie)