Leaf litter/soil components are food. I also occasionally toss in a small vegetable scrap (a potato peel, a few mushroom stumps, etc). I like to think the new smells offer enrichment for the snake.
I also think bacteria and fungi are doing most of the heavy lifting in the clean up crew. And the only thing they should be cleaning up is small amounts of liquid waste and little spots of shed skin. Large waste needs to be manually removed (by you).
Bugs are cool though, and I enjoy the novelty of having some isopods and springtails in the soil. They probably help keep it aerated and I believe they are not harmful to the snake.