Worms naturally and organically unlock minerals from the soil, this is mainly due to the enzymes in their gut, in comparison to the surrounding soil worm cast has in it:
11 x more potassium,
5 x more nitrogen,
7 x more phosphorus,
1.5 x more calcium and
3 x more exchangeable magnesium.
Some worm eggs will filter through your system and end up in the soil where they will hatch. The hatchlings will burrow into the soil allowing the flow of nutrient rich aerated liquid to spread. These worms will generally live in the top 150 to 200mm of the soil and feed on organic matter, excreting the humus so valuable and beneficial to the soil and plants. In short doing as nature intended