Many people here are claiming that it has to try to do with being unambiguously expressive, but many laws are excessively verbose, largely incomprehensible, and still extremely ambiguous, most often in sections that constrain the scope of a law. By contrast some of the most fundamental laws in the nation, the Constitution's Bill of Rights, are generally just a sentence or two - and that works just fine.
In my ever cynical opinion it's largely just a means of accumulating power without accountability. For instance in the terms and conditions of basically all major software now a days it says little more than "You forfeit all rights, we reserve any and all rights imaginable, and we can change this whenever want." But if it actually said this then people might be inclined to say 'hey that's not cool.' But when it's instead wrapped in page after page of incomprehensible legalese, people don't even bother trying to see what they're agreeing to.
In my ever cynical opinion it's largely just a means of accumulating power without accountability. For instance in the terms and conditions of basically all major software now a days it says little more than "You forfeit all rights, we reserve any and all rights imaginable, and we can change this whenever want." But if it actually said this then people might be inclined to say 'hey that's not cool.' But when it's instead wrapped in page after page of incomprehensible legalese, people don't even bother trying to see what they're agreeing to.