It is intsalled because someone does not understand grounding and what ground rods can and cannot do. If the dispenser is already mounted to a concrete base that is in contact withthe earth it is already "grounded". You must run a grounding conductor with the circuit conductors to provide a "ground fault return path." This ground rod then becomes a "supplemental ground". It is not prohibited by the NEC, but it is also not regulated by the NEC. It may be installed in any manner that the specifier requires. It will provide little or no benefit, but will also not cause harm as long as the required equipment grounding conductor is also properly installed. The problem occurs when someone decides that, if a ground rod is installed, then the equipment grounding conductor is not needed; we then have no "low impedence ground fault return path" and violate the section that states that the earth shall not be the only ground return path.
