Esotericists : Without revealing any secrets, can you say why your secret knowledge has to be so?

Answering this Q need not necessarily reveal you as such. You might ‘know someone’ that is.
I was shocked to discover that, even Buddhism has a secret side, that is reserved for the “select few”! Most other religions and traditions do as well.
Why is this?
Is there information that you “just have to be ready for”?
Is there information that would “blow your mind”?
Why the secrecy?
Are some ideas too much to handle, for an insufficiently developed mind or psyche?

Can’t say that I’m holding out much hope for a big response, but here goes.