In most cases, it is possible to convey the same information in a concise manner to the average person.
Just like with math, I get the impression that sometimes the level of jargon/legalese used is an attempt to differentiate oneself from the everyday person. The same information could theoretically be put forward in a way which is understandable to all, not just those with a degree.
From experience, the information provided on gov.uk can be incorrect because it is simplified too much. Very important aspects are lost and it becomes misleading.
As the saying goes, simplify as much as possible, but not more.
Although note that there's a non-zero number of professional linguists and grammarians seem to consider Strunk & White to be prescriptivist nonsense that you're better off ignoring.
Just like with math, I get the impression that sometimes the level of jargon/legalese used is an attempt to differentiate oneself from the everyday person. The same information could theoretically be put forward in a way which is understandable to all, not just those with a degree.