Lawyer and contract-drafting teacher here. The biggest problem with unreadable contracts is that we have too many L.O.A.D.s: Lazy Or Arrogant Drafters. (You can decide for yourself: L.O.A.D. of what?) There's a relevant Dilbert cartoon: [0] To simplify contract language, the biggest bang for the buck comes from SSSP: Short, Single-Subject Paragraphs, which are much easier to read; to review and revise during contract…
In your experience how much of this is attributable to a party of the contract trying to sneak favorable terms into the agreement? Generally I am a fan of Hanlon's razor, assume ignorance/stupidity over maliciousness, but given the nature of the subject matter I am very suspicious.
I've long thought there's sometimes some of that. But I preach to my students that it's not smart to try to sneak something in, buried in a "wall of words," because it presupposes that the other party's reviewer won't spot it and get pissed off.