She reads unsolicited manuscripts only if authors have been referred to her. Authors need someone on their side to make sure their career is growing. That used to be their editor. An editor used to take a job and stay in it until he or she got carried out in a pine box. That doesn't happen now.
Publishers are in business to make money, and they want to pay as little as possible.
I don't feel that publishers are out to cheat authors, not in children's books. I have never had that sense, but neither do I feel that a huge amount of time and thought are given to an author's financial situation. My job is to help my clients grow a career. I am not a one-book agent. If a brilliant manuscript comes my way, I want to see others that the author has written.