Nowadays the emphasis is on pushing the hardware as hard as possible, in what is basically a competition to create the best graphical output on the platform. That means the competitors need to develop their own graphical engines and sometimes go through several iterations until they're satisfied that it's the best they can possibly achieve - by which time there is something better (this is what killed Duke Nukem Forever and will probably kill Gran Turismo 5. Others manage to squeeze a game out if they don't mind making gameplay/content sacrifices, such as what happened with XIII.)
Pushing hardware doesn't mean pushing the graphics alone . I mean
the production process of FF13 in reality isn't as productive as it should be, they end up doing a lot of prototyping during production
for example; Originally there were plans to move characters around the battlefield, It was taken out to increase difficulty.

Graphics are exactly the reason XIII suffered from lack of towns, minigames and sidequests and the developers said so. It isn't impossible to downgrade graphics somewhat in order to add these things and half production time, but they choose not to because they want to entice the casual gamer, which is a bad idea imho.
I respectfully disagree with you, because the main director Toriyama isn't known for pushing the traditional elements, just take a look at Blood of bahamut , FF12:RW and FF13. I can say that even if he released FF13 on PS2 , It will have the same structure.Towns like Eden and Nautilus are already rendered.