That's because Microsoft paid to keep the game exclusive in Europe and North America, according to a Facebook post made by a Namco Bandai community manager.
"Microsoft paid for the exclusivity the same way Sony paid for having Heavy Rain only on PS3," said Namco Bandai community manager Charlotte Toci in a Facebook post caught by RPG Site. Toci's comparison is of course incorrect, as Sony was inherently involved in the development of Heavy Rain, whereas a PlayStation 3 version of Tales Of Vesperia actually exists in Japan. A bizarre comparison.
"It's just one way the business works, sadly," Toci added.
"Those decisions are made really high up y'know, we do try and give them the max of fan feedback, but sometimes it's just out of our hands."
This is really the first evidence we've got of the famous Microsoft "money-hat", which is an irritating business practice. Essentially Microsoft is paid money to keep the game off another platform, which is wholly different from the Heavy Rain comparison in which Sony actually funded the game's development.
That said, Tales Of Vesperia was released so long ago it's hard to manufacture any resentment towards this story.