Castings provide nutrient rich organic matter, along with bountiful microbiology that constantly provides plants the exact nutrients required to thrive.
Because the microbiology provides plants with the exact nutrients it needs, we can expect much higher yields in our plants and gardens with no chemical additions. The microbiology also helps fight pathogens and disease.
Living soils provide proper storage for carbon within our atmosphere. When plants pull in carbon dioxide a portion goes down through the roots, where the microbiology properly stores that carbon dioxide.