Alpha Denzel explained it like the calmness of the sea. "Because this pack doesn't have a Luna. A female beta brings the orderliness a Luna brings."
Adam realized the Alpha's reason for choosing female betas too late. Perhaps, he should have aimed for the Alpha position rather than a position reserved for only a female.
"I'm sorry, Alpha." Remorse sounded in his voice, but what he did was unpardonable. He single-handedly kidnapped Alessia with silver and delivered her to the enemy.
In her own pack where she was supposed to be safe, and even as she held the position of a beta, Adam dared to do this.
"It's too late for that, and in case you don't know, Alessia is my only family. She is my long-lost sister. When she was found, we took her to the Litha Moon Pack to keep it a secret. You bit off more than you could chew, and I would never forgive you."