We need to send papers for you to sign. stuff like non-disclosure agreements etc.
Also, we cant really be sending unreleased games to just anyone, we need some safeguards so we can find and destroy you if you start leaking this on torrent sites
EDIT: Some more explanation. We do give beta access very early. Basically you will be alpha testers, so you arent getting a finished game to test. Usually when you enter about 60% of features are done or such and it gets updated weekly. This is another reason we are quite picky for the initial betas.