I think one reason for the eReader market not being big is that they're so good and sustainable. I bought my Sony PRS-T2 in 2012 and am still using it to this day. It has battery life for weeks, storage space for 100+ books and works just as well as when I bought it. It's really hard for me to motivate buying a new one when the only interesting "new" tech is backlight and I guess it's the same for most eReader owners.

The ~90e I paid for it back in 2012 was for sure good value!