In case of math literature, I'd say it is mainly because the equations would be horribly long. Things like integral computation comes with lots of details, or some kind of long exact sequence. Experts would have trouble understanding it, while normal people almost certainly have no interest in understanding the formulae.

Also, often there is no meaning to the variable. Like, in a real function f(x), x is just "a real variable". There is no additional meaning to it.

As for other fields, I dunno. They might have copied math literature style or something.

I think you can extend this problem to all academic writing. Make it dry, impersonal, formal and fancy. Use big words and long complex sentences, my college English teacher liked to say.

And what a racket the MLA handbook is, huh?

Back when I was in flight school, I was taught how to read Area Forecasts. This is a general outlook of the weather over a large area, say, the American Southeast. They're about a page long and read like this:

SYNOPSIS…LOW PRES TROF 10Z OK/TX PNHDL AREA FCST MOV EWD INTO CNTRL-SWRN OK BY 04Z. WRMFNT 10Z CNTRL OK-SRN AR-NRN MS FCST LIFT NWD INTO NERN OK-NRN AR EXTRM NRN MS BY 04Z.

Synopsis: Low pressure trough at 10:00 GMT in Oklahoma/Texas panhandle area forecast to move eastward into central-southwestern Oklahoma by 4:00 GMT. etc.

Know why they abbreviated it all like that? Because when they first started doing this these forecasts would be distributed by telegraph or teletype. The most common way individual pilots would get this information was to call a flight service station on the telephone and have a briefer read it to them.

We have the internet now; the NWS doesn't publish text Area Forecasts anymore, not for the continental United States anyway. They instead have internet-based animated weather maps which can show observations and forecasts graphically, which is a lot easier to understand than a severely abbreviated block of allcaps.

Explain to me how the MLA or APA rules for formatting citations are any different? "When it's a periodical, you put this part in bold and that part in italics, but when it's an entry in a journal..." Surely there's a way to do this in plaintext with the rule of "list things about your source until you're confident someone else can look it up."

Title: Principles Of Magnetopticalacoustic Levitation In The Comfort And Privacy Of Your Own Bathroom Author: Linus Sebastian et. al. Date of Publication: December 42, 1310 ISBN: 000000000133 Pages referenced: 14-16

You could do this in Notepad, there's no need for an association to make up rules and publish an inch thick reference book, and it would be much more readable to normal non-academics who might want or need the study instead of being so impenetrable there's an industry of writing news article-like summaries of studies that draw conclusions from the study that the study doesn't actually say. Problem with my approach is it killed two parasitic business models which is why it's done the way it's done.