My fast food history is probably like many other middle-class suburban youth: if your parents weren't explicitly against fast food, chances are you ate a lot of it.
For my sister and I, the off-chance of Mom swinging into the McDonald's parking lot after getting picked up from day-care became the most exciting part of the day. This happened on especially long days when she was too tired and hungry to cook. The Golden Arches were a permanent fixture on the skyline since I can remember, and we were fascinated by the bright colors of the Happy Meal toys and the dining room, the strange beeping and commotion in the kitchen, and the delicious smell of salty french fries pulled out of hot oil. As a kid, visiting McDonald's was liberating. Their advertising catered directly to kids, our mother allowed us to make our own food choices, and if we had time, we'd scramble through the Play-place and ball pit after eating.
Even as children, we had no illusions that fast food was healthy, but thinking back, these reasons are probably why fast food has become such a popular option in America.
First, advertising to children is a surefire way to make parents spend money. If a kid knows they have both Chicken McNuggets and Power Ranger toys at a restaurant, they'll ask for it all the time. It's no mystery that despite having no income, children have massive buying power. American parents love to make their kids happy, especially if it's as cheap as a value meal.
Second, Americans love novelty, and fast food chains operate like gum-ball machines. The inside of a McDonald's kitchen looks nothing like the one in your home. It's filled with blinking lights, beeping timers, strange cubbies and compartments and futuristic grills and deep fryers. Although we've been taught this is not the way food should be prepared, it can't be taken for granted that ordering fast food is a minor miracle: a minute after the clerk punches your meal choice into the digital cash register, it's sitting on a tray in front of you, steaming and ready to eat. This is saying nothing of the joy of the drive-through. Not only is fast food delicious, it's engineered to be fun.
Third, fast food is the embodiment of convenience. Americans are obsessed with busyness and packing the most they can into their schedules. Whereas many European societies value personal enjoyment and leisure time, the American mentality follows that the more rushed and hurried you are, the more you're pulling your weight. Unfortunately, this isn't a choice one can opt in and out of; we had a single mother working long hours to support a lean budget. For us and those like us, fast food was often the only available choice when the kids are starving, you haven't had time to grocery shop, and there's nothing substantial in the fridge.
I've never been much farther than Canada, so I can't comment on fast food overseas. Yet here in America, McDonalds is one of our national traditions. Despite fast food's health drawbacks, it is rooted deep in our culture, and I think it's unlikely we'll soon rid ourselves of it.