Ah, you can use them like playing cards, like Magic the Gathering or something similar, but the cards can change when placed on a base. This unlocks game mechanics which aren't possible with only cardboard.

The display is slow because I'm doing a full refresh to prevent shadowing.

If you're used to really quickly animated "e-ink" screens like those on the Pebble watches and Playdate, those are actually memory-in-pixel LCDs. While memory-in-pixel is very low power, it still requires some power at all times, whereas these true e-paper screens hold their image without any power at all.

Also, they're the cheapest displays I could get.

Mmhh but you only get 3 cards right?

Oh, you can buy as many cards as you want. Figuring out how to make a good game without too many cards is definitely a constraint. At $15-20 a card, a 60 card deck is pretty pricey.