You and parent are saying the same thing. Just because they are written for experts does not mean they are not written in an opaque manner.
And as someone who was once in academia, they really are written for 2 reasons:
1. To get past the peer review process.
2. To be written in the minimal time possible.
Enlightening peers comes a distant 3rd.
Example: It took days for a grad student/professor to derive a formula that is included in the paper.
Professor insists the derivation not be included in the paper. Insists the student not even mention in a few sentences the steps to get to it. Claims "any expert should be able to do this. No need to add it to the paper."
It took that expert days to do it. Unless it turns out to be a seminal paper, I guarantee that in most cases, no reader of the paper will even try. An error in the derivation? No one would catch it. Clearly, the professor is not even writing for his peers.
I do agree with the parent - the practices approach that of a guild more than any objective measure of explaining things.
In the sense of presenting the research in a manner that other people can digest, academia seems to be more of a ancient guild than an organisation for expanding knowledge.