In particular, many small worlds were actually not under the control of the Heaven Realm. Ever since the War of the Realms many years ago, the Heaven Realm had lost control over many small worlds.
These small worlds had fallen into the control of other realms. For example, the Demon Realm was controlling many small worlds where humans prospered. They raised the humans like cattle and sheep. When they developed to a certain extent, they would wipe out this small world. Only a small portion of people would be left to rebuild their civilization.
This cycle repeated, and countless humans would die in the mouths of demon beasts.
However, to many big shots in the Heaven Realm, they were not born in the small world. Thus they did not feel anything about such things.