I’m a 6’5" tall guy and being that tall I regard my belly area as the most vulnerable area of my body. If I get attacked with a blade, for example, the attacker most likely be shorter and jab me directly into the belly. And in general, if I get attacked - its most likely that particularly my belly will suffer. And the abdominal area is itself pretty vulnerable, as its not protected with bones and has vitals. And if I get stabbed into the belly - I can either die fast if they hit abdominal aorta or suffer an excruciating pain or sepsis that could result in a slow agonizing death.

Most animals do not expose their bellies in horizontal body position. But humans walking upright do expose that body part. And being tall makes your belly even more exposed relatively to the others.