They're not important enough to the show
on their own , so the only reason we would see such an event would be in service to others' plots (in this case, Alexis's, perhaps Curtis and Jordan's). Plus, the idea of a "civil union" sounds so un-romantic and clinical that I can't imagine soap producers managing to make it on par with a soap wedding. I'm not even sure what a civil union entails, other than signing paperwork. Does the ersatz-bride toss the ball-point pen rather than a bouquet?
So yeah, they would need some sort of "floor show" to make it worth filming, and I'm sure Drunk Alexis busting her uptight daughter for being a 'ho would make it a great Friday episode.