People who buy the Alpha have access to the Beta and get a copy of the full game upon release.

Think of the possibilities for the PC version of future Elder Scrolls games with a modding community as big as "ours". The opportunities for large scale bug testing, finding which game play elements work and which fall flat, UI refinements, quest line order and pacing, ...spell making and other lost/omitted features revisited because they were given a few thousand extra hands to work on.

...it is a pretty grand "What if...?"

Because the Alpha of a TES game would be near unplayable.

It doesn't have to be a real Alpha, it can be a Beta they can just call "Alpha".

...some would argue that Oblivion, Fallout and Skyrim were all released Betas anyway.