This is a quote from the great Leo Burnett. Leo Burnett was one of the true legends of Advertising whose work includes the Marlboro Man, Tony the Tiger, and many others. Leo Burnett is now an international company that produces some of the best advertising going round.
Some of the best advertising is successful as a result of having this simplicity at its heart. The target viewing audience for a lot of advertisements often lack the time or effort to fully consider the ad in front of them. This is why the most simple ads, the ones with a single driving message, will often produce the greatest effect.
Below is one of my favourite ads from Leo Burnett, so simple.