You make an excellent point. With the prevalence of DRM and ownership, someday you might not be able to read your book, either due to old unsupported device or

You make an excellent point. With the prevalence of DRM and ownership, someday you might not be able to read your book, either due to old unsupported device or a format, or even the company going bankrupt. Even if neither of this happens, at some point the standards will change. If you don't use the "cloud" and risk the lockout, you will probably need to backup you information. The hardware changes, physical books don't. This is a worry for some.