Corn gets digested. The “corn” you see in your poo after eating sweet corn is usually a empty hull, the good stuff has been digested and only the tough fibrous hull is left. Hard corns are upper-mid in their amount of calories per volume when compared to other grains.
What am I missing here, this is way too obviously strange to me, gotta be missing something.
The main reason of “why corn” is that corn is a staple food, meaning that in many regions of the world (including the US) it supplies a large amount of the calories a person eats to get through their day. This includes many areas where subsistence agriculture is common. As such in some countries a subsistence farmer may grow corn and most of what he eats throughout the year is that corn. Obviously, this is not a ideal diet and malnutrition becomes a common problem, like say anemia.
Also corn uses C4 photosynthesis, which is much more efficient than the C3 photosynthesis most crops use. Which means (depending on conditions) you can get more grain per acre.
Edit: I just noticed that I typed “substance” rather than “subsistence”… twice. Fixed now.