Is having the ground rod enough for the electric panel, or must you have it also at the house side of the water meter?
If the water pipes are metal, they like both around here.
I think a lot has to do with the age of the install.
Older systems seem to just have the water line ground. Then when the electrician updates the service he needs to install the proper exterior ground rod. Some areas require 2 exterior ground rods.
I helped my electrician when he changed out my FPE. I did the all the grounding.(With him making sure I did it right)
Driving the rod 8 feet in clay in the summer is no fun!
I also used a #6 gauge copper continuos from the street side of the meter to the box.
If I only see one or the other I recommend improving the system.
Again I am no expert. Just trying to help.
A supplemental grounding electrode is recommended, but not always required. If I remember correctly, it has to do with the resistance back to the utility.
Most new construction in my area uses two electrodes - typically a water line and a Ufer.