Because prestidigitation has a more specific meaning than "magic." And that is how the disease creeps into academic discussion. When focused on minutae, the fine gradations of meaning become important. But over time it becomes a habit that is hard to break and there is a certain pleasantness to creating a vocabulary that is only understood by those in the know.
The Sokal Hoax was an example of these tendencies taken to their horrible conclusion. I'd include my copy of
The Sokal Hoax: The Sham that Shook the Academy when I send you your books but it is from my pseudoscience and junk science collection so it is only available for loan. If by any chance you're interested in it and you'd give it back, I'd be happy to send it.
As for 25-cent words, I once used "paucity" in an extemporaneous presentation back in grad school to much grief. But such things just happen to me naturally. Still don't know why it got such a reaction since I used it correctly.