Some use big words to try to intimidate those who might not be able to understand them. I always find it funny when people use this language with me, as if I can't find a dictionary.
This alienates people into distrusting any information that could be helpful, even if it's written in difficult language.
Some researchers, writers, and speakers use jargon from their line of work so often that they aren't aware of how difficult it is for those outside that bubble to decode the language.
My brother, father, and cousin are all retired defense specialists, and their acronyms and jargon are so familiar to them that no one outside of the defense industry knows what they're talking about.