Why Rhodium?

Unfortunately, silver oxide is typically contaminated with sulfur and other contaminants making it not quite so good a conductor as you might think

Regarding rhodium being "too hard" for good outlet contact, that is completely flawed logic.  The base metal will determine the softness of the metal contact, not a layer of rhodium  a few molecules thick.

Conductivity of different mEtals....

https://www.effectrode.com/knowledge-base/conductivity-of-metals-sorted-by-resistivity/

As you can see rhodium is not a good conductor, but it is relatively affordable and it is tough and looks shiney

Regards

Um, rhodium is the most expensive commodity precious metal.

Give me bare copper every time.

Granted, it’s more expensive than gold per troy ounce.

However the thickness of the rhodium plating tends to be much thinner than gold plated parts, making it more affordable than gold.

Silver is still the best from a conductivity perspective but prone to wear and tarnishing

Regards