Good luck coming up with karma-points-based explanations for all the pleasure and suffering in the world. What did the caterpillar do to deserve getting paralyzed and eaten alive by wasp larvae?
A crude example: A man torturing a caterpillar for fun, may have to take birth in a life of caterpillar and endure the same pain, either by a human or different species.
Thanks for the good question, am open to more.
I don't believe this explanation, but reincarnation usually comes along with karma in a package.