Games are so much more complex now that it takes a much greater number of people to think of new ways to break things and exploit them, etc. As such, what is called beta is really just private alpha with the small group of testers and release is public beta.
Few companies have the wherewithal to have a group of testers so large that they can release a game that has any designs on greatness, but doesn't need some pretty substantial patching.
Just the nature of the modern beast, imho.