Why is there still so much academic gibberish?
There's one of my papers, much of which is couched in seriously obfuscated language: in places, even worse than the example linked by OP. (I won't say which paper, in case I embarrass my co-authors.)  In my case, I think the reasons were:

More than a decade elapsed between production of the first complete draft of the paper and its submission to the journal where it was eventually published.  During that period, we changed our minds several times about some of the core conclusions; but each time, some bits of explanatory text got left in the paper that were only really apposite in the context of now-obsolete conclusions.
During that period, my co-authors and I were not in very frequent contact, and we ended up using edits to the text of the paper to communicate with each other about the science in the paper; this produced text that was sub-optimal for communicating with readers.
Despite the long total drafting period, the submitted version was finalized in a tearing hurry to meet a deadline for a thematic issue of the journal, so there was no time for a thorough pass through the text for clarity and concision.
Perhaps most significantly of all: the referees let us get away with it.