Also Steam works well because it really isn't easy for the common consumer to copy a Steam game vs. as easy as it would be to copy a single unencrypted movie file to share casually with their friends. It is much easier to buy a movie on this Steam type clone and then put it online or give it to everyone you know, which the industry won't want.
Until you get a Steam like service written for OSX, Linux, Windows, Android, iPhone and streamable via the web with proper copy protection this will not fly.