A document written by literate people, for the digestion of many, using common language conventions and employing correct grammar- yes, I can see why. The ideas are radical, but the language is clear and consistent.
Perhaps the key to not losing your writing job in an AI-dominated era is to keep the perplexity high.
The language of the Constitution is anything but clear and consistent, in fact it's often purposely vague.
Entire schools of legal philosophy have formed around, and gotten into brawls over, the implications of the comma in the incomplete first clause of the Second Amendment, for instance.
No, the language is very clear and simple, the issue is that clear and simple language is woefully inferior to legalese when it comes to eliminating semantic ambiguity. In the case of the second amendment's comma usage, it was actually grammatically correct at the time, but English has changed since then, thus highlighting another issue with plain language. Similarly, the phrase "thou shall not kill" is very clear and simple, but people have spent millenia trying to figure out how to handle countless edge cases.
Perhaps the key to not losing your writing job in an AI-dominated era is to keep the perplexity high.