Unfortunately Jets/Rubies sounds gendered to a lot of people: while "Jet" is a jemstone, it's also an engine, a plane, sports team, and a fictional gang, all more male-ish than female-ish. And "Ruby" is a commonish female name and gemstones are more associated with women than men.
There's also a lot of benefit in having terms with "L" and "R" to tie the role names to the roles.
It's definitely harder for experienced dancers and callers to switch from Ladies/Gents to Larks/Robins than to Jets/Rubies, but as someone who helped their dance switch over (and who considered Jets/Rubies at the time) people got the new terms pretty quickly. It's a total non-issue at our dance now.
Jeff