I fully agree! I'm also disappointed (but not surprised) that kobo (or some other 3rd party epub seller) hasn't created an API where you register a key pair (or whatever) and can decrypt books on your devices. I suspect it's based on publisher demands. Ironically, this is one place where a blockchain might be useful - sales are recorded on it, contracts are written with respect to it, and if the publisher goes belly up users can run nodes to maintain it.