Why?

As to Cosmo Canyon as a whole, I feel it's generally not as much a bother being force-fed exposition about the Planet AVALANCHE is trying to save, but being forced to escort Nanaki down to the Canyon's gritty unders was just epically not awesome. It served no point other than to give Nanaki some form of backstory and drive which I suppose the same could be said of Barret at Gold Saucer but Barret had been a core member from the beginning of the game. Nanaki could just as easily been made into a wandering character like Shadow from FF6. Still, I think Barret's story along with Cid's were both integrated pretty seamlessly into the core plot. The Cloud-Tifa-Aerith story pretty much was the core plot. Nanaki is the only one with whom I feel they said, "we need an excuse to give Red XIII a backstory, let's have their Buggy break, force-feed them some exposition and then force them to go on a quest which has nothing to do with the rest of the story." I mean, at least Barret's story with Dyne still was connected to ShinRa. Nanaki's story didn't have that going for it. It was just utter... I don't know what to call it. It wasn't even an infodump... because there really was nothing else to learn after leaving the observatory. There was no point to going down there.