“If only people were rational, then…” will probably be followed by facts, reasons evidence that, if given to a completely rational person, would change their behaviour.

But we know that not everybody thinks or acts rationally. Or, we know that it is not possible – due to human nature to be influenced by our emotions – to be perfectly rational (nor perhaps is it desirable).

So if we wish to influence behavior, we need not only facts (which as argued somewhat above have limited effect) but also other things – stories, appeals to human emotion – that are largely the domain of creativity, art and story telling.