While they are often used for back-handed compliments or humor, Double Negatives are generally discouraged in communication because they can be difficult to untangle: "Never have I owed nothing to no one."
But what about negatives? I think those can be a problem too.
Take for example my GPS, which gives the following warning if there's a toll road in the route it has calculated:
The problem with this message (and I say this having pressed the wrong button on multiple occasions) is that it takes a bit of thought to figure out which button to press! The answer to a simple question: "Do you want to use toll roads" has been made needlessly complicated by adding a sentence, and switching the response.
"The current route involves toll roads" is the first sentence. Most people would expect that it's asking; "do you want to use this route" (i.e. the toll roads?) after all, that's what it just said it came up with. So this immediate instinct is to click 'Yes," not "No."
But then it switches the question around with the second sentence, and frames it as a negative "Do you want to avoid the toll roads" or put another way "Do you not want to use that route?"
Either way, you have to stop for a second and think about what it's asking.
It would have been so much simpler - and less prone to operator error - if it had just asked: "Do you want to use toll roads"