Plain English: What is it good for?

I think everything should be written in plain English. But when I push plain English, what I'm really aiming at is legal text that must be read and understood by nonlawyers:

Insurance policies
Website disclaimers
Credit-card agreements
Jury instructions

And more. But I don't try to impose plain English on my students who are learning to write memos and briefs. I save it for the advanced class in which they will write client letters and ticket disclaimers.

If we could bring plain English to multi-million-dollar transactional documents and appellate briefs, that would be great. But right now we can't even bring it to jury instructions in death-penalty cases. We have a ways to go.