Jargon exists because specialists in a subject want to communicate quickly among themselves, instead of paraphrasing all the time. I'm a mathematician, if I had to use plain-English words instead of jargon in my papers, I would go insane. But my papers aren't meant for the general public (although they're welcome to read them), they're meant for a specialist audience. This is not the case of government websites.
Jargon exists because specialists in a subject want to communicate quickly among themselves, instead of paraphrasing all the time. I'm a mathematician, if I had to use plain-English words instead of jargon in my papers, I would go insane. But my papers aren't meant for the general public (although they're welcome to read them), they're meant for a specialist audience. This is not the case of government websites.