In workshops, nobody argues against plain English, but it's a different matter when we look at examples from the participants' own organisations. That's when the defences come out. They worry that writing in simple, everyday language will create the wrong impression.
Maybe you've recognised the problem.
You suspect that your readers are skimming your text. They don't notice that you want them to reply to your email today. They don't discuss your report in any detail - just the recommendations.