For me it was all about the taste. Why do you grow your own food? Here is a study that looked at nutrient loss from UC Davis.

I live in the DFW area in Texas. I started raising worms a year ago this past Sept.. I started with 5# in two 30 gallon tubs. I now have 50 - 60 pounds in two 8’x2.5’ cft bins. My plan is to start marketing castings for the upcoming growing season. I can produce about 150# of castings a week at my current level. I use horse manure, wood shavings and spent mushroom substrate for food and bedding. My journey with worms began as a way to better utilize the horse manure produced by our horses. In the learning process I discovered that commercial farming is destroying our topsoil and that worm castings can help rebuild the soil. It is now my goal to grow my operation to a large scale that can produce quality worm castings and liquid casting extracts to be used by gardeners, commercial greenhouses and farmers.