I'd say it's more that God/Light bestowed past planets with life, too, but some of them didn't appreciate the gift.
Reincarnation is important because it allows you to understand multiple fields of life. Even if you don't REMEMBER being a fish, that experience is important because it gave you and your Soul a greater grounding in the world itself. As a human, you look at the fish you're eating, and accept that while it is a different existence than you, it is a shared existence that allows you to continue to exist. You were eaten as a fish to grow a human. Now, as a human, you are eating a fish to grow. In this way, we push each other forward.
The issue with reincarnation is some people are too arrogant to accept death/rebirth, and want to live forever as "Gods".
This is a problem because they NEED to keep reincarnating in order to learn about the world around them.
The beings that cut themselves out of this reincarnation cycle are destroying their own spiritual progression to fuck with everyone else's, because they're scared of death and want to play God, by stealing energy to cheat death.
This is how I more or less view "Demons": entities that tried to escape physical reincarnation by becoming energy itself, and feeding off of others. Lot of Japanese series touch on this. Shadows in Persona; Bleach; I believe Shiki (haven't watched it but heard good things).
The saddest part of all of this is that God still loves them, and the biggest thing holding them back is being unable to accept that God would forgive them if they honestly tried to change. They've spent so much time acting like evil shitty fake gods, the idea that the real God could still love and forgive them is incompatible with their current level of consciousness.
Their false sense of superiority has corrupted their minds entirely.
