I don't have the comment saved nor do I remember exactly which Live Letter or Q&A it was mentioned in, because it was alllll the way back in early SB or maybe even HW, so it's vague enough in my memory that I can't recite it verbatim so take it with a grain of salt if it makes you feel better- but Yoshida had stated that they do not want to make another companion because of the spaghetti codehow "complicated" it is/was to program another "pet" that can be programmed with different stances and a skill tree, and that creating another leveling system for another companion was essentially "too complicated" or "too time-consuming."

Like already mentioned, it just seems to be another neglected and abandoned system created early-on in the game (like Squadrons, among other things), and the devs only acknowledge it in the sense that despite not being interested in improving it, they do still like to create paper doll outfits for chocobos as content "rewards."

But. But... With how they seem to be continually investing resources into single-player-proofing the game ("we added Duty Support to a 10 year-old ARR dungeon guys! look how productive we are!"), I wouldn't give-up hope completely. Maybe later down the line (sooner rather than later at this point <_<; ), when XIV has kind of hit where XI is right now (with low activity necessitating dozens of Trust NPCs), the need for another companion might arise... And then they'll magically somehow be able to implement one then.