You're confusing ownership of media with ownership of copyright. I'm not suggesting that I can buy an mp3 and reshare it (or the same for an ebook), that's a violation of copyright. I've never suggested that buying them lets me remove DRM, re-share, etc. It's a strawman argument that you and conciselyverbose seem very attached to, but not an argument I'm making.
Ownership is not strictly limited to physical items, and I'm very curious why people think it is. There's significant outstanding case law precedent that proves that ownership can apply to digital files as well.