Why the secrecy? In my opinion, fraud and danger. First of all, implied secrets make great masks for fraud and/or incompetence. As for danger, those who get results see some of the risks and, if virtuous, don't want to be responsible for harm to, or through, others by sharing/teaching too much too soon - and with the wrong people. Evil and mental illness are not fantasies and Esoterics magnify character flaws - and virtues.