And as I’ve seen trans people explain it, I just think of “cis” as a shorthand way of saying “not trans.” It’s not an identity, necessarily, just a descriptor, to put the two (trans and non-trans) on an equal basis, and not have a rhetorical paradigm in which “normal,” non-trans, people are just “people,” whereas trans people are the only ones set apart with an adjective. Like “straight” as opposed to “gay.” Until gay people started using “straight” to mean “not gay,” it didn’t have that meaning in common usage. As I recall, it once was used as “straight people” vs. drug users. Or “straight” people vs. the counterculture.