Beta Key Dispersment

Hello,

I have opted in for beta testing for the last 4 xpac's. I am disappointed that i have not yet ever received an invite to test the beta of an expansion. My question is even though people have opted in for beta testing how does blizzard choose who gets the keys? Is it as random as mount drops in game or is there a systematic thing i keep missing to make me more of a candidate for this prestigious oppurtunity?

Please Help

I didn't find the right solution from the internet.

References:-
us.battle.net/forums/en/wow/topic/20763606179
B2B Online Content Marketing

Thanks