Plants get most of their structure by pulling in carbon from the atmosphere and using it to make more plant. Regenerative organic farming generally works to keep that captured carbon in the soil, by using excess plant matter as soil amendment, to put it simply. From what I have seen this has the potential for massive carbon retention over chemical intensive industrial farming which generally does not focus on the use of organic matter as soil amendment.
Good soil has benefits but plants don't get carbon from their roots. They make sugar in the leaves and make that into more complex molecules for growing.
The plants get carbon from the atmosphere of course, but retaining organic matter in the soil, which captures that carbon, has other value.
"Soil organic matter significantly improves the soil's capacity to store and supply essential nutrients (such as nitrogen, phosphorus, potassium, calcium and magnesium), and to retain toxic elements. It allows the soil to cope with changes in soil acidity, and helps soil minerals to decompose faster."