"With software, either the users control the program (free software) or the program controls the users (proprietary or nonfree software)." - Richard Stallman
Note: When I say "free software", I refer to freedom, not price.
First off, my nature as a programmer (if that was natural at all!) seems to be the reason, but you guess not. Regular users should be concerned about software freedom before powerusers and hackers. Hop into gnu.org if you want to learn more.
1) In the beginning, all software was essentially free. That's the way it should be. But for some reason, some people started to introduce a new concept of software development: software property, copyrighted binaries and later "software patents", leading to proprietary software existence.
2) All software that ever existed has started as free software, but then it's up to the developer to turn it nonfree (unethical conduct) or keep it free. There is no irregularities in this fact.
3) While the free software movement and the open source camp still do not agree on a mutual word to describe the good type of software (free software vs. open source software), they certainly agree upon a word that descibes the bad type of software (proprietary). And that has much to say how the two camps are essentially sharing the same enemy.