2012 era Nook eink reader playing a game with hacked refresh:
https://www.youtube.com/watch?v=9fbD753xE-U
The tech can do better, but as I've heard it told, the market for it has been eink readers. Who needs to refresh their book at 120hz? is the thinking. Folks that want to game or have a "retina" resolution buy a tablet proper.
Upping refresh has steep power costs too. Ereader marketers like their "recharge once every 6-8 weeks!" message.