[samhw]

It's not just the strict denotative meaning. It's also the valence and emphasis of the statement. It doesn't concentrate the mind on "what if it disappears?", but on "how likely is it to disappear?", to which the (supposed; bullshit) answer is 'not likely'. Someone might - on rational analysis - know what it means, and still come away with a better impression than if they said it outright.