Now, though, the Festival is almost as much about brands as it is about agencies - not just because the link between creative quality and advertising effectiveness has been proved irrefutably, but because the event has also evolved into a forum for learning rather than creative back-slapping.
So one of the most prestigious awards handed over in the Palais later this month will be the Creative Marketer of the Year gong. This year it goes to Coca-Cola, a company that is having to dig deep into its creative resources and marketing expertise to tackle what will perhaps prove the biggest challenge in its history: the rage against sugar (although Coke's famous formula now uses high fructose corn syrup, not cane sugar, in the US) and the contribution of soft drinks to the obesity epidemic.
Coca-Cola's chief executive, Muhtar Kent, issued a statement setting out four global business commitments to "further contribute to healthier, happier and more active communities", including a promise to withdraw advertising activities aimed at children under the age of 12.
Quite how that will be defined, monitored and enforced, and when it will take effect, we don't yet know, but together the pledges form the single most-important marketing initiative the company will take over the next few years.
They're also a tangible sign that Coca-Cola, increasingly moving on from its austere, secretive and arrogant corporate culture, is now ready to face the health lobbyists with a positive agenda before further sanctions are imposed. In truth, it has little choice in the longer term. But as all our pieces on Coca-Cola this month illustrate, one of the world's most successful marketing-led companies has begun to review, revitalise and sometimes reject entrenched practices; the brand that has shaped popular culture clearly now recognises the imperative of moving with it.
For other brands heading off to Cannes this month, forget the back-slapping and take a close look at the lessons to be learned from the Creative Marketer of the Year.
claire.beale@haymarket.com