The indigenous physique of this world is too peculiar, even could be described as 'magical', as if it was meticulously designed, with a focus on the body before one's life.
A box that's not broken can neatly contain a large amount of solid energy. Once broken, the soul, like a bag, can carry away potentially uncontrollable solid energy.
Moreover, Hell in this world possesses an immense amount of energy. It's incredibly difficult for the dead to resist Hell's pull. After death, it's like packaging dangerous materials, taking them to a recycling station called Hell for processing.
If Hell in this world didn't have such vast energy to pull away souls with strong energy, the world wouldn't be so chaotic.
Because the difference in capacity between the box and the soul bag is not significant.
Indigenous people in soul state can fight as much as they could when alive; this distinction doesn't make them stronger or weaker. If the body is weak, its role in combat becomes negligible.
