That's nothing compared to what some people had to deal with e.g. surviving famines. That takes some serious mental fortitude, but I would imagine after that experience you'd be perfectly fine if dinner was served late. If you ever read Siddartha, there's this part where the protagonist learned how to fast with the Samanas in the forest, and not everyone knows how to deal with that sensation and accept it as just another sensation in life.
On the other hand, I know people who get into this bizarre state if they are hungry, not long after whatever their normal mealtime might be sometimes. People joke around about being "hangry" but its a real thing for some people. I can see how if you haven't learned how to accept the sensation of hunger, and all you know with that feeling of hunger through your life is to immediately satiate that sensation, sticking to a caloric deficit would not be easy.
You are also correct - caloric deficit is not very sustainable long term for a large number of people.
There is ongoing study to figure out why — for example, why some people are much less able to stick to a diet, or have constant food cravings, and so on. That’s not at odds with what you’re questioning. The focus is on those areas because the requirement of a caloric deficit for weight loss is one of the most reliable observations we have so far.