ifixit did a teardown where they briefly speculated on this and I think they nailed it.

This and the humane piece of shit are, at least partially, trying to avoid app store regulation/rules. Apple have basically always been assholes and google are speedrunning that to the point it is genuinely obnoxious to buy kindle books if you use a cell phone at all.

Combine that with trying to sell a new form factor device (similar to smart watches and the like) and it makes sense. Even if the products themselves are still rather meh.