Peculiar insularity

What is the source of the peculiar insularity of literary “theorists”?

What do I mean by “peculiar insularity”? It’s that people in other fields know that the jargon of their fields is jargon. They know it has to be translated for people not in their fields, and that most people are not in their fields, and that it seldom makes sense to assume a random pool of strangers will be all or mostly people in their fields. What is it about literary “theorists” that causes them to fail to know that, or, worse, to fail to act on it despite knowing it?

As far as I’ve ever been able to figure out, it’s just a form of vanity, but why it’s so peculiar to that one segment of the university, I don’t have even a guess.