Because everybody lives in Manhattan? The world is a lot larger than just the US, and even in the US if you've moved out of Manhattan (say to one of those suburbs) and you have a family of four to feed you'll be surprised how much month there is left at the end of your money as a single earner.
Overfeeding is more related to what you eat than the money you spend on it, in fact it is easier to overfeed on cheap food than it is on better grade food.
Well, of course it's easier to overfeed on cheap food; you don't run out of money as quickly, and unsurprisingly, the food with the most calories per dollar is also the food that contains the most calories per gram: pure fats and carbohydrates. (Pure alcohol and protein are a bit more expensive, I'll admit, but even pure gluten is pretty cheap.)
Food in the US is much more expensive in the majority of the world. I imagine that in the Netherlands it's even more expensive. Still, home-cooked adequate nutrition in the US costs a great deal less than junk food. McDonald's, Popeye's, and Frito-Lay can't even come close to competing with dried corn, dried beans, dried brown rice, soybean and canola oil, potatoes, squash, onions, collards, carrots, ramen, eggs, multivitamins, oranges, bananas, molasses, oatmeal, and the occasional spinach, lettuce, tomato, and cucumber.
(This was even true when I lived in a poor inner-city black neighborhood in Dayton, where everything in the supermarket cost more, and you couldn't take the carts out into the parking lot. Supermarket prices were a lot cheaper in the rich neighborhoods, and I went to Aldi maybe once a month to stock up on the stuff that was cheap there.)
You have to be smart and fairly industrious to cook. If you can't hold down a job, odds are you can't cook well enough to make it a serious value proposition over pre-packaged and restaurant fare.
No, you don't have to be smart to cook. I don't know if you even have to be smart to cook well. I suspect not, because I learned to cook good food pretty quickly; someone who was even dumber than I am might take a little longer, but it still wouldn't be a substantial fraction of a human lifespan.
It does take work, but not a huge amount of work, especially if the aim is to feed your family, not to cook well. Oranges and bananas, you don't even have to cook. A peanut-butter sandwich is two minutes if you already have bread and peanut butter. Cooking brown rice or lentils involves dumping a measuring cup into a pot three or four times and setting a timer. Same thing's true of eggs, oatmeal, polenta, ramen, and grits. Other beans, you have to dump into a pot of water the night before, and you probably ought to sort them so you don't bite a rock, which might take five or ten minutes for a big pot. A big pot of beans and a big pot of rice can satisfy the caloric and protein needs of a family of four for a few days.
And if you dump garlic, onions, butter, soy sauce, salt, pepper, mayonnaise, and hot sauce on any random barely-edible non-sweet crap, you can get it up to the level of McDonald's or Popeye's pretty quick.
There are some cheap foods that require a lot of work. Collards are a pain. Baking your own bread may be cheaper than buying it in a store‚ but it's a lot of work. And about any vegetable you use in a dish is gonna need some slicing. But it doesn't require you to be "industrious" at the level of digging a ditch for eight hours, or working overtime at the bubblebath factory they can't afford to heat.
Now, it's true you aren't born knowing this stuff. You have to learn it, and even if you know it in theory you may not be in the habit of putting it into practice. The soft-drink aisle and the potato chips are pretty tempting. Stopping in at McDonald's on the way home from school is a lot more immediate than stopping at Jewel Osco for a loaf of bread and some peanut butter, even if you evade the peanut butter. And if you've just gotten off your split shift at the call center and you have a couple of kids to feed before you start in on your homework, it's pretty hard to motivate yourself to cook. I'm not trying to minimize the difficulty of being poor in the US.
I'm just saying the problem with food is not that good food is out of reach.
I'm just saying you have to be able to hold down a job well enough that food is not the primary cost driver for your living expenses. You don't have to be at a HN-level of intelligence/industriousness to do that either, but you do have to be reasonably intelligent.
If you can't hold down a decent job, odds are you aren't going to be much use in the kitchen.
Overfeeding is more related to what you eat than the money you spend on it, in fact it is easier to overfeed on cheap food than it is on better grade food.