Way back around 2010-11 someone posted that someone had done (slow) video on e-ink.
1) the displays are expensive (relatively) for their size
2) Color is even more expensive

3) Slow

4) Some folk can't get past the black 'flash'
5) Week long battery life with Greyscale has little marketing flare.
I think there are many applications where stingy battery usage would be an advantage. The issue is CHEAP, always wins (for consumer products. Remember the $400 Toilet seat?)