Plants and the beneficial soil microorganisms they depend on were created, developed and/or evolved together. They have a symbiotic relationship. Plants take the Sun's energy and, through photosynthesis, combine it with water and nutrients to form the sugars which become the energy source for all other living organisms, including the microorganisms. About half of the sugar/energy produced by the plant goes into the root system of the plant. About half of that sugar/energy is released by the roots into the soil by design. The plant naturally feeds the microorganisms it and they need to be healthy.
These now well fed microorganisms do a multitude of good things for the plant and soil in return. Just a few examples are: Increasing nutrient availability, reducing salt levels and EC, increasing resistance to diseases and other pests, increasing CEC, reducing soil compaction, improving water infiltration, reducing thatch accumulation, etc. Ultimately the plant and the microbes want the same soil conditions. But only the microbes, not the plant, have the ability to directly improve the soil. The overall result of the carbon fertilization approach is that you are still providing all the NPK etc. that your plants need AND you are feeding the beneficial microorganisms in the soil. This is in no way 'Bugs in a Jug'. Simply adding more microbes does not do the same thing. If those microbes could live there, they would already be there. The limiting factor is how many beneficial microbes the soil can sustain.
Shifting your fertilization practices to include more organic carbon naturally promotes more microbial activity. It works, it's the law of nature. The limiting factor is the amount of sugar/energy available to support microorganisms. So instead of adding bugs, add bug food - stable organic carbon.
Benefits of Soil Microorganisms