That is absolutely not true. There's no bigger fan of jokes and jabs w/in constraints than lawyers, and judges in particular. I know of several law schools which have competitions amongst their classes to find the weirdest, funniest, or most bizarre citation or footnote w/in legal briefs/case law.

There is some weird stuff in our legal system, however they (typically) are asides amongst the core arguments, or in support of the core arguments of a legal case.

Remember that good lawyers are hackers. They're trying to find edge cases and tease at the margins of the representation of the world that has been encoded in law.