On the other hand (and I'm slightly playing Devil's advocate here), books and other physical media go out of print eventually. It can become difficult to find a copy of some archaic technical manual that interests you. (Anyone selling any Symbolics manuals? :-))
There is no reason for a digital publishing to stop creating new copies of a digital work (once they finally develop an economic model that works.)
There is no reason for a digital publishing to stop creating new copies of a digital work (once they finally develop an economic model that works.)