Both pipes should be at the same electric potential (ground) since
they are both are buried.
The grounding is done to help ensure the electrical panel has a true
ground.
In some cases the panel ground is wired to a long steel pole driven
into the earth. Just different ways to do the same thing.
Brad

blueman wrote:
When we had our electric service upgraded, the electrician (as
expected) ran a ground wire from the cold water main inlet to the
ground on the panel.

I read somewhere that one should also run a similar grounding wire to
the natural gas pipe inlet but the electrician didn't do that.
- Is it required by code?
- Is it recommended?
- Should one use the same gauge wire as for the water pipe?
- Any special considerations?
- Can I daisy chain it from the water pipe or do I need to run a
separate ground back to the panel?

Thanks