Not surprising, the game is too westernized for Japan (probably japanese people felt that SE were so obviously trying to cater to the western audience and they didn't liike that) + Japan doesn't care about home console games + any damage the FFXIII series could have done (though I'm not sure if FFXIII was hated in Japan as much as it is in the west).
P.S. Final Fantasy 6 on SFC deserved more sales than the others