I don't know about their marketing strategy, but I think I know why he didn't eat the roll at McDonald's. Alison Lurie wrote recently in the New York Review of Books about several of Alain de Botton's books, focusing especially on recently published The Architecture of Happiness. Lurie quotes a passage in which the author ducks into a London McDonald's and succumbs to a generalized sense of dread.
The setting seemed to render all kinds of ideas absurd: that human beings might sometimes be generous to one another without hope of reward; that relationships can on occasion be sincere; that life may be worth enduring.... The restaurant's true talent lay in the generation of anxiety. The harsh lighting, the intermittent sounds of frozen fries being sunk into vats of oil and the frenzied behaviour of the counter staff invited thoughts of the loneliness and meaninglessness of existence in a random and violent universe.The footnote leads to Lurie's comment suggesting the feeling was no accident.
 De Botton's experience, while exaggerated, is not atypical. As is well known, McDonald's restaurants are deliberately designed both to attract customers and to discourage them from lingering, in order to produce what is known in the trade as "maximum throughput." The bright colors and the huge shiny photographs of high-calorie food draw people in; but the noisy acoustics, glaring overhead lights, small crowded tables, and uncomfortable seats encourage customers to leave as soon as they have finished what is appropriately called "fast food."Or before they finish. Maybe even before they start. Anything to get away from the existential dread that makes even a cube farm seem warm and welcoming.