Interviews with the Final Fantasy XIII development team appear to have yielded some surprising revelations, including the admission that the game’s notoriously linear structure was due in large part to the trouble inherent in designing towns in a “high definition” manner.
The revelations come by way of developer interviews and other information published in Square Enix’s official Final Fantasy XIII production Final Fantasy XIII Scenario Ultimania.
Some of the most interesting points are paraphrased below:
The game’s linearity was just because depicting towns and so on like we did before was impossible to do on an “HD” console – it was too much work.
Nomura had hardly anything to do with it; he just did character design and commercials, not even the intro or movies.
The game was designed with DLC in mind but we don’t actually have any planned.
It was easy to port to the Xbox. Porting to the PS3 is harder. The PS3 has more processing power but you have to do it properly.
Jumping was manual at first and you could jump onto the titans.
You used to be able to avoid enemy attacks in the field using the analogue stick, but due to difficulty considerations it was canned.
The battle team came up with the transforming summons. The art team was dead against them.
“I was thinking this time we would make it completely story-centric” – Toriyama.
There is a source, but the link is NSFW therefore, I'm not posting it.
The revelations come by way of developer interviews and other information published in Square Enix’s official Final Fantasy XIII production Final Fantasy XIII Scenario Ultimania.
Some of the most interesting points are paraphrased below:
The game’s linearity was just because depicting towns and so on like we did before was impossible to do on an “HD” console – it was too much work.
Nomura had hardly anything to do with it; he just did character design and commercials, not even the intro or movies.
The game was designed with DLC in mind but we don’t actually have any planned.
It was easy to port to the Xbox. Porting to the PS3 is harder. The PS3 has more processing power but you have to do it properly.
Jumping was manual at first and you could jump onto the titans.
You used to be able to avoid enemy attacks in the field using the analogue stick, but due to difficulty considerations it was canned.
The battle team came up with the transforming summons. The art team was dead against them.
“I was thinking this time we would make it completely story-centric” – Toriyama.
There is a source, but the link is NSFW therefore, I'm not posting it.
Maybe if it had been on the PS2 they could have added side quests. The game may be boring if there are no on-the-side things to do. This is not good news 

If it was too much work then they should've focused on other things then just the graphics. Linear isn't nearly as fun then games with extra things added on. Now i'm mad
and I was having a good day too. >.>