Gold does not oxidize the way silver does, and that property serves a structural purpose in gold over silver: the exterior layer shields the silver base from the oxidation process that would otherwise cause tarnishing.
Care & Keeping
The plating layer is thin, and abrasion from direct contact with other metal surfaces cuts through it faster than normal wear: soft pouches and lined compartments eliminate that friction entirely.
Style Notes
If she wears jewelry to work, travels frequently, or worries about her accessories catching on clothing or hair, the closed structure of hoop earrings make them a practical everyday choice.