Dan is FFXIII een zee zonder water ben ik bang
lees en huiver
en dan met name dit stukje
The more important thing to understand is that, the very first time you access a save point (contextualized in-game as a kind of nifty holographic computer terminal thing), the three options are "Save" "Shop" and "Quit." "Quit" doesn't mean "quit the game" — it means quit the save point menu. "Save" means save the game. "Shop" means — yes, enter the shop.
So, there's your first clue: You shop from the save point menus. Whoa. Have you solved the mystery yet?
Here it comes — I'll be gentle: No towns.
You gasp! Sadly, the only towns you see in the first great big chunk of Final Fantasy XIII are destroyed, dilapidated, filled with monsters. The major story MacGuffin is intimately tied to this floating Utopia called Cocoon, which some religious organization sees fit to regularly purge of shady individuals, so in order for this story to work, basically no towns in the "outside" world is kind of a given. Of course, the existence of a utopia doesn't precisely guarantee that all the world outside said utopia consist of straight lines in which large objects regularly fall, obstructing the path backward. Though there's a reason for that, too.