This is absolutely correct. I have had to issue "cease and desist letters" (albeit informal ones done without a lawyer; they were typed by myself) to a few online users who have attempted to post my work without permission. Some of this work was uncredited and the works that were credited were often drafts that I may not be selling for profit now but may choose to at a later point in time.
Likewise, some software developers may be planning to update or re-release a work at a later date. Consider Nintendo, for example, who has created a "virtual console" on the Wii with games going back 23 years that have been released for new generations to enjoy. Nintendo has also updated some classic games and re-released them (such as when Super Mario Bros. 3 was released for Game Boy with new graphics and sound). There is also copyrighted code that may not be obsolete in new releases simply because it is still being used (such as a routine from, say Office 98 that may still be used in Office 2008).
Granted, there are some who have released their works (Apple in regards to System 6.0.8 and Cliff Johnson in regards to his old games are two notable examples) or wanted them to be free in the first place. However, not everyone can exist in a "utopia" world where ideas can be freely shared simply because, for some of us, there is a fear that someone will take the idea, patent it, copyright it, and sell it themselves. (This is why I do not permit my novel draft to be distributed online--someone could easily take it, put their name on it, and sell it).