I was talking with one of the cashiers at my gamestop and she brought up a good point. Why were they pushing people to pre-order so they got access to the beta only to open it up to everybody? I, along with many other people, felt "exclusive" playing the beta, and then anybody could play it. I don't know, just my opinions, what are yours? Edit: ok I get the fact that they wanted the maximum amount of people to test the game and experience it so they would eventually buy it. But I still feel the "exclusivity" was lost, I can't say "yeah I played the beta!" as did 4.5 million other folks did
The biggest reason is a major stress test. There were four point six million people playing the beta at its peak and that is only the rough estimate. Needless to say there will be way more on day one and they needed to have some kind of idea on how to be prepared in the slightest.