It is but social convention.
About the only things that stick are "don't stop physical and mental activity as you age" and "do stuff in moderation".
If you call it "intermittent fasting" and write a book about it, you can get a whole movement behind how healthy skipping breakfast and lunch is. And another movement preaching about how bad it is. And a followup book about what you REALLY should do ad nauseam.
As for good diets, for instance, there is a wild meal schedule that has shown to be fairly good at managing weight, it is just intense. It is the 16 to 17 meals a day plan. One meal every hour you are awake, each one only about 100 to 150 calories. It does potentially work but try selling it to people and worse getting folks to stick to it.
not designed, evolved
Social behavior and the actual behaviors themselves evolved through populations as, among other things, an information storage mechanism that survives generations.
surely the natural response here will be about how important, healthy, and real this particular fad is. same as all the other health fads everyone would talk about for the last hundred years