SAVE MONEY
This is probably the most important incentive for people to eat fast food. Fast food is usually much cheaper than homemade meals and dine-in restaurants. Because of that, it is the most common meal choice of lower class folks in our societies.
Having said that, fast food is eaten by almost everyone. Some of the most popular athletes in the world eat fast food. Even our president eats fast food here and there. It is definitely not limited to poor people, despite the way the media portrays it.