There are many, you're just not seeing them because they're probably out of your usual tech bubble. Check goodereader.com for their eReader reviews. They often review eReaders which are running Android with web browsers in it, recently they reviewed a couple eInk smartphones, including a color eInk one.
There is a lot going on in the eReader world but it is at the fringe of the tech bubble of SV. It is in Europe and Asia, specially Asia.
The usual FAANG companies don't want you using that stuff because it moves you away from their silos and platforms. If you start using a device to read books away from their profiling disguised as social interaction, away from their ad machines, and walled garden shops, they lose money. Oh boy, that sounded way more conspirational than I wanted. What I want to mean here is that since these type of eReaders do not favour major tech companies from the USA, they're usually not covered in their platforms or news media that follows SV stuff.