Having been poor, its very cheap per hour as a luxury, something you saved up for. Compared to going to a movie, or a bar, its very cheap both in an absolute sense or per hour. I'm not sure where one can go out for an hour while having dinner that's cheaper.
One issue is due to income inequality most of the population is poor. Perhaps 19 in 20 of their meals are eaten at home, but that 1 in 20, multiplied by most of the population, equals very full McDonalds. Middle and upper class people have this weird idea that most poor people meals are eaten at McDonalds but some simple math about restaurant seats per sq mile just doesn't work. Even poor people like the occasional luxury, its just theirs is a hamburger as opposed to a cashmere sweater or a new car.
A second issue is the usual middle/upper class disconnect from poor people combined with a lack of prediction or creativity. Why if poor people can't afford to cook at home and thus "have to" eat at restaurants all the time because thats so much cheaper, then the restaurant business in Somalia or Haiti must really be booming. What did people eat before fast food in the 70s?
The urge that you report is sugar related. Everything is drowned in carbs, mostly HFCS. Buns today taste sweeter than Hawaiian sweet rolls did when I was a kid. I suspect Hawaii rolls are no longer sold because its impossible to add more sugar to sugar saturated regular 2016 dough. I eat pretty low carb normally, and I feel the same way about cookies or anything else sugary, suddenly three days later I gotta have another chocolate chip cookie. Sugar is addictive.
Finally its a HN trope that home cooking is too expensive and impossible and no one on the planet does it. I donno its like automobile analogies on slashdot or something. Its just a belief, and you show allegiance to the site and its mores by social signalling your agreement with it. Yes yes we all know the numbers don't add up, but like I wrote, its a belief, and nobody ever reasoned themselves either into or out of a belief.