Soil resistivity surveys provide useful information about the ways a ground mass will discharge electrical current. Soil resistivity can dramatically impact the performance of conductors with lower resistance grounds offering improved discharge performance, and higher resistance offering worse discharge performance. Think of it like this, gold is one of the best conductors in the world (which is why it often appears in computer components) but if you put it in rubber it wouldn't discharge current at all. Knowing at which depth optimal resistivity is located may help designers and installers of electrical earthing / grounding systems optimise their conductor configuration.