DRM is security theater at this point. It's easy to find any book in any format on the internet. Amazon perpetuates this myth to authors and publishers that without DRM their book will be everywhere for free (which it already is), but all it does it keep them locked to Amazon out of fear.
The problem for the vast majority of authors isn't theft, it's that no one ever discovers their book at all.
The problem for the vast majority of authors isn't theft, it's that no one ever discovers their book at all.