The third option is "because they don't want to be blamed for model error". Governments aren't necessarily competent, but you can try to get them to understand 5%/95% confidence intervals, at least in hindsight. If you publicly release a prediction, and then the real outcome is the 10% confidence line, you're probably going to be yelled at for being wrong regardless of the error bars.

Of course, if the center of the prediction is horrifying, "people don't understand confidence intervals" then becomes a case of avoiding societal breakdown.