Ever had a craving? They just come out of nowhere. You'll hear someone say "I feel for some KFC", "I want a Whopper", "I'm feeling for a Pepsi". I wonder how many a marketer rejoices when they hear such utterances.
While hunger is physiological, a craving is more psychology than physiology. Studies have suggested that food cravings start in the mind, with strong mental imagery being a key component. That's the reason the branded food photos look so darn good - that's going to produce a strong, vivid image when a craving comes around. Plaster the company logo all over it and voilà, instead of craving a burger, you're gonna crave a Whopper!
Spend enough money on advertising and you can get into the minds of people, and then their pockets. You'll keep them coming back, even though the food is never as good as in the ads, and the customer service rep never smiles half as much as on TV.