I (unfortunately) think you'll find that this was due to it being in beta. Hopefully I'm wrong and the community stays relatively decent, but I'm not confident in it yet.

I seriously doubt that anyone who wanted to play the game a week ago couldn't find a beta key floating around somewhere to play (there are about a million key giveaways on reddit, etc). I think that Valve getting rid of the beta status is more about them being confident that it's polished than wanting to release to a broader audience.