I'm not sure what the issue is. They let people use the keys and the beta keys are limited but they aren't limited to how many people can use them. When beta testing is done they can kill those limited number of keys. Only having a limited number of keys used for public beta testing makes things far easier to keep track of. The keys are so easily accessible that it's silly and if you downloaded the ISO from Microsoft for the OS then there is no reason why one couldn't also get the beta key.
Microsoft isn't asking for anything special or beyond acceptable. You are entitled to your opinion, of course, Xie, but I really can't understand your somewhat overblown anger (?) with the situation.