Because it didnt look and didnt feel like a hallway.
You know, I've been thinking about the contrast a bit more. I'd say in terms of pure mechanics, FFX was as much a corridor as XIII was, except it was a two way corridor.
In terms of narrative on the other hand, the biggest difference is that FFX's party are lauded by the people in that world, since they're seen as heroes
and no one talks about Yuna being a sacrifice lol
they land on a planet with virtually no people left
I think while everything from writing (dislikeable characters yadda yadda) to pacing have some to do with it, the difference in reception of the party mandated by the setting is a big reason FFXIII feels so... desolate, for lack of a better word. When you're on the run, it makes less sense to be able to travel backwards.
Palompolum in particular really hammers that point home.
also HD towns are hard
edit: Even the sequels continue that trend. In FFX-2, Yuna is pretty much seens as a hero even while being a bit of a rogue. FFXIII-2... yay time travel, hard to give a shit about people who're going to be long-gone the moment you move forward in the narrative. LR, world is ending, almost everyone couldn't give two hoots about what happens anymore.
Still, Academia in XIII-2 was pretty damn atmospheric, and LR was actually pretty fun in all the complete nutjobs you did bear-ass fetch quests for.