Board Thread:General Discussion/@comment-30881771-20180816134353/@comment-29325824-20180816143251

Actually, there is a Hell in Bleach. And also Hueco Mundo. And even if you ignore the souls that get devoured by Hollows or destroyed by Quincy, there is still the fact that souls do die in Soul Society, which causes them to reincarnate in the Human World. It's called the "flow of Souls".

It's in fact a crucial point of the setting that there must be a balanced amount of Souls in the human world and the Soul Society at any given time. If too many souls happen to be in one place compared to the other, the worlds would collide with each other and be destroyed.