…unless they help you grow into a fuller human being and understand your role in the Universe.
That doesn’t rhyme very well, but I’m finding that it sums up my opinion of oathbound (aka secret) knowledge in religion. I was listening to a discussion in which the consensus was reached that secret knowledge is basically unnecessary. I disagree. Having participated in oathbound rituals, I will fervently support the movement to keep some wisdom out of the public eye.
Much of the “secret” material I have become privy to is kept thus because it would lack weight and meaning, were it revealed in any other way. It would lack context, and thus cease to be meaningful. This wisdom becomes valuable by the sheer fact that it is not widely distributed. Without that veil, it becomes nothing. It is the act of being given this wisdom – the context in which it is imparted – that infuses it with power.
Meaning is something that humans often make of the random happenings around us. I have recently suffered through a really rough period of a few weeks. I chose, initially, to attribute all of this to my gods. I blamed Them, and my lack of attendance in shrine due to occupational conflicts, for the pain I was experiencing. I’m still not certain I don’t believe that, but I have also attributed the meaning of these events as a realigning of my life more fully into Ma’at, like the splinting of a broken bone. Similarly, meaning is what we make it, in terms of sacred secrets. We can experience wisdom in a sacred context that would never hold any weight in a secular revelation, and thus attribute deep, holy meaning to it.
I won’t say that there are no sacred secrets which are simply kept because group members feel the privilege should only belong to certain people, or to control others. It does happen, and that is a clear abuse of the spiritual relationship formed between students of a religion and its teachers. This should not mean that true wisdom, a true experience of sacred oathbound knowledge, should be discredited entirely. When appropriate, it is never done to exclude. It is never done to shame those who have not yet partaken of the experience. When appropriate, the secrets are kept so that at the right time, each devotee may have a transformational moment, in which they are blessed with an understanding of themselves, their spirituality, and the nature of whatever sacred secret has been revealed.
carrying their light 
I see enough people on the web who grab something out of context and run with it, thinking they can order the NTR around like servants with some little spell. The more I see of that, the more utility I see in secrets.
It certainly looks like there was an initiatory/mystical tradition in ancient Egypt, and some of that got transferred to the mystery cults of Greece and Rome.