There are many people who believe in the idea of corporate social responsibility and therefore think that fast food firms should market healthier choices more aggressively. However, firms’ main responsibility is to make money for their shareholders. If they can make money by marketing healthy food, they should. If they can make more money marketing less healthy food, though, that is exactly what they should do.
Corporations do not bear the responsibility for acting in ways that are good for people. Instead, they are responsible for creating supply to fulfill legal demands. So long as it is legal for people to eat unhealthy food (and so long as they wish to do so), it is the fast food industry’s responsibility to give them what they want. If we, as a society, want people to eat healthier, we should either pass laws requiring them to do so and/or we should pass laws requiring restaurants to serve healthier foods. Until we do so, it is not fair to expect fast food firms to lose money by aggressively marketing foods that people do not want and which are not as profitable for those firms.