Everyone who deals with legal documents can point to unintelligible agreements. Many would argue that this is the aim of the drafter.That may sometimes be the case. But, more often, the drafter(s) in question simply know no better. Most lawyers are NEVER taught how (or why) to draft in Plain English.
If you're interested in removing ambiguity and communicating more clearly, there are a couple of sites you should check out.
And for an interesting take on the proliferation of legal gobbledygook in contracts, see Why Our Agreements Look Like Crap.
Automated document assembly software can help keep your contracts consistent and compliant, but the document author still must use clear, understandable language.