There are several reasons to take a soil and bedrock sample. This is often requested by businesses, farmers, and homeowners. The good news is that sample drilling is quicky and not terribly expensive even though it does take a bit of time to haul the tractor with its long drill bit out there. The sample taker can extract the core, which might even be ejected with air pressure. The even sample allows for samples from every depth.
A farmer is likely interested in the topsoil, but subsoil and the bedrock source are as important because they help to explain the mineral composition. A farmer might want to know if the soil is shallow or if the bedrock contains useful minerals. A construction company might need to know where the bedrock layer in order to build a basement or foundation. Homeowners might want to dig a well or some other structure.