It's more interesting to differentiate the social meanings of "private" and "secret": When I send a letter in an envelope, it's private. It's not for your eyes. It might not be secret, however, because I might not mind the information in the letter being publicly revealed.

That distinction between "private" and "secret" is something the opponents of encryption forever try to erase, by claiming that things which are not secret should not be private, which has the effect of making privacy suspicious by default, instead of unremarkable. It's the snail-mail equivalent of trying to shame everyone into sending their mail using postcards, so someone who sends "a lot" of envelopes is now a target of suspicion, for some arbitrary definition of "a lot" which changes based on context.

I disagree with you. Encryption deals with privacy. Steganography deals with secrecy.

It's still private, it is no longer a secret. It hovers somewhere between being a 'public secret' or 'public knowledge' without the general public being aware of it because it hasn't been published yet. And in that sense the real world is very much different than the web, there everything that is not explicitly protected is published.